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fd5b820d | 1 | = Git User Manual |
99eaefdd BF |
2 | |
3 | Git is a fast distributed revision control system. | |
4 | ||
02783075 | 5 | This manual is designed to be readable by someone with basic UNIX |
2de9b711 | 6 | command-line skills, but no previous knowledge of Git. |
d19fbc3c | 7 | |
2624d9a5 BF |
8 | <<repositories-and-branches>> and <<exploring-git-history>> explain how |
9 | to fetch and study a project using git--read these chapters to learn how | |
10 | to build and test a particular version of a software project, search for | |
11 | regressions, and so on. | |
ef89f701 | 12 | |
2624d9a5 | 13 | People needing to do actual development will also want to read |
aa971cb9 | 14 | <<Developing-With-git>> and <<sharing-development>>. |
6bd9b682 BF |
15 | |
16 | Further chapters cover more specialized topics. | |
17 | ||
d19fbc3c | 18 | Comprehensive reference documentation is available through the man |
b3d98887 | 19 | pages, or linkgit:git-help[1] command. For example, for the command |
1249d8ad | 20 | `git clone <repo>`, you can either use: |
d19fbc3c BF |
21 | |
22 | ------------------------------------------------ | |
23 | $ man git-clone | |
24 | ------------------------------------------------ | |
25 | ||
b3d98887 CC |
26 | or: |
27 | ||
28 | ------------------------------------------------ | |
29 | $ git help clone | |
30 | ------------------------------------------------ | |
31 | ||
32 | With the latter, you can use the manual viewer of your choice; see | |
33 | linkgit:git-help[1] for more information. | |
34 | ||
2de9b711 | 35 | See also <<git-quick-start>> for a brief overview of Git commands, |
2624d9a5 | 36 | without any explanation. |
b181d57f | 37 | |
99f171bb | 38 | Finally, see <<todo>> for ways that you can help make this manual more |
2624d9a5 | 39 | complete. |
b181d57f | 40 | |
b181d57f | 41 | |
e34caace | 42 | [[repositories-and-branches]] |
fd5b820d | 43 | == Repositories and Branches |
d19fbc3c | 44 | |
e34caace | 45 | [[how-to-get-a-git-repository]] |
fd5b820d | 46 | === How to get a Git repository |
d19fbc3c | 47 | |
2de9b711 | 48 | It will be useful to have a Git repository to experiment with as you |
d19fbc3c BF |
49 | read this manual. |
50 | ||
5162e697 | 51 | The best way to get one is by using the linkgit:git-clone[1] command to |
a5f90f31 BF |
52 | download a copy of an existing repository. If you don't already have a |
53 | project in mind, here are some interesting examples: | |
d19fbc3c BF |
54 | |
55 | ------------------------------------------------ | |
4b9ced27 | 56 | # Git itself (approx. 40MB download): |
d19fbc3c | 57 | $ git clone git://git.kernel.org/pub/scm/git/git.git |
4b9ced27 TK |
58 | # the Linux kernel (approx. 640MB download): |
59 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git | |
d19fbc3c BF |
60 | ------------------------------------------------ |
61 | ||
62 | The initial clone may be time-consuming for a large project, but you | |
63 | will only need to clone once. | |
64 | ||
283efb01 TK |
65 | The clone command creates a new directory named after the project |
66 | (`git` or `linux` in the examples above). After you cd into this | |
d19fbc3c | 67 | directory, you will see that it contains a copy of the project files, |
0c4a33b5 | 68 | called the <<def_working_tree,working tree>>, together with a special |
1249d8ad | 69 | top-level directory named `.git`, which contains all the information |
0c4a33b5 | 70 | about the history of the project. |
d19fbc3c | 71 | |
e34caace | 72 | [[how-to-check-out]] |
fd5b820d | 73 | === How to check out a different version of a project |
d19fbc3c | 74 | |
a2ef9d63 BF |
75 | Git is best thought of as a tool for storing the history of a collection |
76 | of files. It stores the history as a compressed collection of | |
2de9b711 | 77 | interrelated snapshots of the project's contents. In Git each such |
a2ef9d63 | 78 | version is called a <<def_commit,commit>>. |
d19fbc3c | 79 | |
0c4a33b5 BF |
80 | Those snapshots aren't necessarily all arranged in a single line from |
81 | oldest to newest; instead, work may simultaneously proceed along | |
57283291 | 82 | parallel lines of development, called <<def_branch,branches>>, which may |
0c4a33b5 BF |
83 | merge and diverge. |
84 | ||
2de9b711 | 85 | A single Git repository can track development on multiple branches. It |
0c4a33b5 | 86 | does this by keeping a list of <<def_head,heads>> which reference the |
5162e697 | 87 | latest commit on each branch; the linkgit:git-branch[1] command shows |
81b6c950 | 88 | you the list of branch heads: |
d19fbc3c BF |
89 | |
90 | ------------------------------------------------ | |
91 | $ git branch | |
92 | * master | |
93 | ------------------------------------------------ | |
94 | ||
4f752407 BF |
95 | A freshly cloned repository contains a single branch head, by default |
96 | named "master", with the working directory initialized to the state of | |
97 | the project referred to by that branch head. | |
d19fbc3c | 98 | |
81b6c950 BF |
99 | Most projects also use <<def_tag,tags>>. Tags, like heads, are |
100 | references into the project's history, and can be listed using the | |
5162e697 | 101 | linkgit:git-tag[1] command: |
d19fbc3c BF |
102 | |
103 | ------------------------------------------------ | |
104 | $ git tag -l | |
105 | v2.6.11 | |
106 | v2.6.11-tree | |
107 | v2.6.12 | |
108 | v2.6.12-rc2 | |
109 | v2.6.12-rc3 | |
110 | v2.6.12-rc4 | |
111 | v2.6.12-rc5 | |
112 | v2.6.12-rc6 | |
113 | v2.6.13 | |
114 | ... | |
115 | ------------------------------------------------ | |
116 | ||
fe4b3e59 | 117 | Tags are expected to always point at the same version of a project, |
81b6c950 | 118 | while heads are expected to advance as development progresses. |
fe4b3e59 | 119 | |
81b6c950 | 120 | Create a new branch head pointing to one of these versions and check it |
328c6cb8 | 121 | out using linkgit:git-switch[1]: |
d19fbc3c BF |
122 | |
123 | ------------------------------------------------ | |
328c6cb8 | 124 | $ git switch -c new v2.6.13 |
d19fbc3c BF |
125 | ------------------------------------------------ |
126 | ||
127 | The working directory then reflects the contents that the project had | |
5162e697 | 128 | when it was tagged v2.6.13, and linkgit:git-branch[1] shows two |
d19fbc3c BF |
129 | branches, with an asterisk marking the currently checked-out branch: |
130 | ||
131 | ------------------------------------------------ | |
132 | $ git branch | |
133 | master | |
134 | * new | |
135 | ------------------------------------------------ | |
136 | ||
137 | If you decide that you'd rather see version 2.6.17, you can modify | |
138 | the current branch to point at v2.6.17 instead, with | |
139 | ||
140 | ------------------------------------------------ | |
141 | $ git reset --hard v2.6.17 | |
142 | ------------------------------------------------ | |
143 | ||
81b6c950 | 144 | Note that if the current branch head was your only reference to a |
d19fbc3c | 145 | particular point in history, then resetting that branch may leave you |
81b6c950 BF |
146 | with no way to find the history it used to point to; so use this command |
147 | carefully. | |
d19fbc3c | 148 | |
e34caace | 149 | [[understanding-commits]] |
fd5b820d | 150 | === Understanding History: Commits |
d19fbc3c BF |
151 | |
152 | Every change in the history of a project is represented by a commit. | |
5162e697 | 153 | The linkgit:git-show[1] command shows the most recent commit on the |
d19fbc3c BF |
154 | current branch: |
155 | ||
156 | ------------------------------------------------ | |
157 | $ git show | |
e2618ff4 BF |
158 | commit 17cf781661e6d38f737f15f53ab552f1e95960d7 |
159 | Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)> | |
160 | Date: Tue Apr 19 14:11:06 2005 -0700 | |
161 | ||
162 | Remove duplicate getenv(DB_ENVIRONMENT) call | |
163 | ||
164 | Noted by Tony Luck. | |
165 | ||
166 | diff --git a/init-db.c b/init-db.c | |
167 | index 65898fa..b002dc6 100644 | |
168 | --- a/init-db.c | |
169 | +++ b/init-db.c | |
170 | @@ -7,7 +7,7 @@ | |
d19fbc3c | 171 | |
e2618ff4 BF |
172 | int main(int argc, char **argv) |
173 | { | |
174 | - char *sha1_dir = getenv(DB_ENVIRONMENT), *path; | |
175 | + char *sha1_dir, *path; | |
176 | int len, i; | |
177 | ||
178 | if (mkdir(".git", 0755) < 0) { | |
d19fbc3c BF |
179 | ------------------------------------------------ |
180 | ||
181 | As you can see, a commit shows who made the latest change, what they | |
182 | did, and why. | |
183 | ||
35121930 | 184 | Every commit has a 40-hexdigit id, sometimes called the "object name" or the |
1249d8ad | 185 | "SHA-1 id", shown on the first line of the `git show` output. You can usually |
35121930 BF |
186 | refer to a commit by a shorter name, such as a tag or a branch name, but this |
187 | longer name can also be useful. Most importantly, it is a globally unique | |
188 | name for this commit: so if you tell somebody else the object name (for | |
189 | example in email), then you are guaranteed that name will refer to the same | |
190 | commit in their repository that it does in yours (assuming their repository | |
191 | has that commit at all). Since the object name is computed as a hash over the | |
192 | contents of the commit, you are guaranteed that the commit can never change | |
193 | without its name also changing. | |
194 | ||
2de9b711 | 195 | In fact, in <<git-concepts>> we shall see that everything stored in Git |
35121930 BF |
196 | history, including file data and directory contents, is stored in an object |
197 | with a name that is a hash of its contents. | |
d19fbc3c | 198 | |
e34caace | 199 | [[understanding-reachability]] |
fd5b820d | 200 | ==== Understanding history: commits, parents, and reachability |
d19fbc3c BF |
201 | |
202 | Every commit (except the very first commit in a project) also has a | |
203 | parent commit which shows what happened before this commit. | |
204 | Following the chain of parents will eventually take you back to the | |
205 | beginning of the project. | |
206 | ||
2de9b711 | 207 | However, the commits do not form a simple list; Git allows lines of |
d19fbc3c BF |
208 | development to diverge and then reconverge, and the point where two |
209 | lines of development reconverge is called a "merge". The commit | |
210 | representing a merge can therefore have more than one parent, with | |
211 | each parent representing the most recent commit on one of the lines | |
212 | of development leading to that point. | |
213 | ||
5162e697 | 214 | The best way to see how this works is using the linkgit:gitk[1] |
2de9b711 | 215 | command; running gitk now on a Git repository and looking for merge |
ddd4ddef | 216 | commits will help understand how Git organizes history. |
d19fbc3c BF |
217 | |
218 | In the following, we say that commit X is "reachable" from commit Y | |
219 | if commit X is an ancestor of commit Y. Equivalently, you could say | |
02783075 | 220 | that Y is a descendant of X, or that there is a chain of parents |
d19fbc3c BF |
221 | leading from commit Y to commit X. |
222 | ||
e34caace | 223 | [[history-diagrams]] |
fd5b820d | 224 | ==== Understanding history: History diagrams |
d19fbc3c | 225 | |
2de9b711 | 226 | We will sometimes represent Git history using diagrams like the one |
d19fbc3c BF |
227 | below. Commits are shown as "o", and the links between them with |
228 | lines drawn with - / and \. Time goes left to right: | |
229 | ||
1dc71a91 BF |
230 | |
231 | ................................................ | |
d19fbc3c BF |
232 | o--o--o <-- Branch A |
233 | / | |
234 | o--o--o <-- master | |
235 | \ | |
236 | o--o--o <-- Branch B | |
1dc71a91 | 237 | ................................................ |
d19fbc3c BF |
238 | |
239 | If we need to talk about a particular commit, the character "o" may | |
240 | be replaced with another letter or number. | |
241 | ||
e34caace | 242 | [[what-is-a-branch]] |
fd5b820d | 243 | ==== Understanding history: What is a branch? |
d19fbc3c | 244 | |
81b6c950 BF |
245 | When we need to be precise, we will use the word "branch" to mean a line |
246 | of development, and "branch head" (or just "head") to mean a reference | |
247 | to the most recent commit on a branch. In the example above, the branch | |
248 | head named "A" is a pointer to one particular commit, but we refer to | |
249 | the line of three commits leading up to that point as all being part of | |
d19fbc3c BF |
250 | "branch A". |
251 | ||
81b6c950 BF |
252 | However, when no confusion will result, we often just use the term |
253 | "branch" both for branches and for branch heads. | |
d19fbc3c | 254 | |
e34caace | 255 | [[manipulating-branches]] |
fd5b820d | 256 | === Manipulating branches |
d19fbc3c BF |
257 | |
258 | Creating, deleting, and modifying branches is quick and easy; here's | |
259 | a summary of the commands: | |
260 | ||
1249d8ad | 261 | `git branch`:: |
df47da75 | 262 | list all branches. |
1249d8ad TK |
263 | `git branch <branch>`:: |
264 | create a new branch named `<branch>`, referencing the same | |
df47da75 | 265 | point in history as the current branch. |
1249d8ad TK |
266 | `git branch <branch> <start-point>`:: |
267 | create a new branch named `<branch>`, referencing | |
268 | `<start-point>`, which may be specified any way you like, | |
df47da75 | 269 | including using a branch name or a tag name. |
1249d8ad | 270 | `git branch -d <branch>`:: |
df47da75 TA |
271 | delete the branch `<branch>`; if the branch is not fully |
272 | merged in its upstream branch or contained in the current branch, | |
273 | this command will fail with a warning. | |
1249d8ad | 274 | `git branch -D <branch>`:: |
df47da75 | 275 | delete the branch `<branch>` irrespective of its merged status. |
328c6cb8 | 276 | `git switch <branch>`:: |
1249d8ad | 277 | make the current branch `<branch>`, updating the working |
df47da75 | 278 | directory to reflect the version referenced by `<branch>`. |
328c6cb8 | 279 | `git switch -c <new> <start-point>`:: |
1249d8ad | 280 | create a new branch `<new>` referencing `<start-point>`, and |
d19fbc3c BF |
281 | check it out. |
282 | ||
72a76c95 | 283 | The special symbol "HEAD" can always be used to refer to the current |
1249d8ad TK |
284 | branch. In fact, Git uses a file named `HEAD` in the `.git` directory |
285 | to remember which branch is current: | |
72a76c95 BF |
286 | |
287 | ------------------------------------------------ | |
288 | $ cat .git/HEAD | |
289 | ref: refs/heads/master | |
290 | ------------------------------------------------ | |
291 | ||
25d9f3fa | 292 | [[detached-head]] |
fd5b820d | 293 | === Examining an old version without creating a new branch |
72a76c95 | 294 | |
328c6cb8 NTND |
295 | The `git switch` command normally expects a branch head, but will also |
296 | accept an arbitrary commit when invoked with --detach; for example, | |
297 | you can check out the commit referenced by a tag: | |
72a76c95 BF |
298 | |
299 | ------------------------------------------------ | |
328c6cb8 | 300 | $ git switch --detach v2.6.17 |
95f9be55 TA |
301 | Note: checking out 'v2.6.17'. |
302 | ||
303 | You are in 'detached HEAD' state. You can look around, make experimental | |
304 | changes and commit them, and you can discard any commits you make in this | |
328c6cb8 | 305 | state without impacting any branches by performing another switch. |
95f9be55 TA |
306 | |
307 | If you want to create a new branch to retain commits you create, you may | |
328c6cb8 | 308 | do so (now or later) by using -c with the switch command again. Example: |
95f9be55 | 309 | |
328c6cb8 | 310 | git switch -c new_branch_name |
95f9be55 | 311 | |
ca69d4d5 | 312 | HEAD is now at 427abfa Linux v2.6.17 |
72a76c95 BF |
313 | ------------------------------------------------ |
314 | ||
a6e5ef7d | 315 | The HEAD then refers to the SHA-1 of the commit instead of to a branch, |
72a76c95 BF |
316 | and git branch shows that you are no longer on a branch: |
317 | ||
318 | ------------------------------------------------ | |
319 | $ cat .git/HEAD | |
320 | 427abfa28afedffadfca9dd8b067eb6d36bac53f | |
953f3d6f | 321 | $ git branch |
95f9be55 | 322 | * (detached from v2.6.17) |
72a76c95 BF |
323 | master |
324 | ------------------------------------------------ | |
325 | ||
326 | In this case we say that the HEAD is "detached". | |
327 | ||
953f3d6f BF |
328 | This is an easy way to check out a particular version without having to |
329 | make up a name for the new branch. You can still create a new branch | |
330 | (or tag) for this version later if you decide to. | |
d19fbc3c | 331 | |
e34caace | 332 | [[examining-remote-branches]] |
fd5b820d | 333 | === Examining branches from a remote repository |
d19fbc3c BF |
334 | |
335 | The "master" branch that was created at the time you cloned is a copy | |
336 | of the HEAD in the repository that you cloned from. That repository | |
337 | may also have had other branches, though, and your local repository | |
66a062a1 MM |
338 | keeps branches which track each of those remote branches, called |
339 | remote-tracking branches, which you | |
1249d8ad | 340 | can view using the `-r` option to linkgit:git-branch[1]: |
d19fbc3c BF |
341 | |
342 | ------------------------------------------------ | |
343 | $ git branch -r | |
344 | origin/HEAD | |
345 | origin/html | |
346 | origin/maint | |
347 | origin/man | |
348 | origin/master | |
349 | origin/next | |
350 | origin/pu | |
351 | origin/todo | |
352 | ------------------------------------------------ | |
353 | ||
66a062a1 MM |
354 | In this example, "origin" is called a remote repository, or "remote" |
355 | for short. The branches of this repository are called "remote | |
356 | branches" from our point of view. The remote-tracking branches listed | |
357 | above were created based on the remote branches at clone time and will | |
1249d8ad | 358 | be updated by `git fetch` (hence `git pull`) and `git push`. See |
66a062a1 MM |
359 | <<Updating-a-repository-With-git-fetch>> for details. |
360 | ||
45dfd403 JN |
361 | You might want to build on one of these remote-tracking branches |
362 | on a branch of your own, just as you would for a tag: | |
d19fbc3c BF |
363 | |
364 | ------------------------------------------------ | |
328c6cb8 | 365 | $ git switch -c my-todo-copy origin/todo |
d19fbc3c BF |
366 | ------------------------------------------------ |
367 | ||
1249d8ad | 368 | You can also check out `origin/todo` directly to examine it or |
45dfd403 JN |
369 | write a one-off patch. See <<detached-head,detached head>>. |
370 | ||
2de9b711 | 371 | Note that the name "origin" is just the name that Git uses by default |
d19fbc3c BF |
372 | to refer to the repository that you cloned from. |
373 | ||
374 | [[how-git-stores-references]] | |
fd5b820d | 375 | === Naming branches, tags, and other references |
d19fbc3c BF |
376 | |
377 | Branches, remote-tracking branches, and tags are all references to | |
f60b9642 | 378 | commits. All references are named with a slash-separated path name |
1249d8ad | 379 | starting with `refs`; the names we've been using so far are actually |
f60b9642 | 380 | shorthand: |
d19fbc3c | 381 | |
1249d8ad TK |
382 | - The branch `test` is short for `refs/heads/test`. |
383 | - The tag `v2.6.18` is short for `refs/tags/v2.6.18`. | |
384 | - `origin/master` is short for `refs/remotes/origin/master`. | |
d19fbc3c | 385 | |
f60b9642 BF |
386 | The full name is occasionally useful if, for example, there ever |
387 | exists a tag and a branch with the same name. | |
d19fbc3c | 388 | |
1249d8ad | 389 | (Newly created refs are actually stored in the `.git/refs` directory, |
fc74ecc1 BF |
390 | under the path given by their name. However, for efficiency reasons |
391 | they may also be packed together in a single file; see | |
5162e697 | 392 | linkgit:git-pack-refs[1]). |
fc74ecc1 | 393 | |
c64415e2 BF |
394 | As another useful shortcut, the "HEAD" of a repository can be referred |
395 | to just using the name of that repository. So, for example, "origin" | |
396 | is usually a shortcut for the HEAD branch in the repository "origin". | |
d19fbc3c | 397 | |
2de9b711 | 398 | For the complete list of paths which Git checks for references, and |
f60b9642 BF |
399 | the order it uses to decide which to choose when there are multiple |
400 | references with the same shorthand name, see the "SPECIFYING | |
9d83e382 | 401 | REVISIONS" section of linkgit:gitrevisions[7]. |
d19fbc3c | 402 | |
aa971cb9 | 403 | [[Updating-a-repository-With-git-fetch]] |
fd5b820d | 404 | === Updating a repository with git fetch |
d19fbc3c | 405 | |
3c735e07 JM |
406 | After you clone a repository and commit a few changes of your own, you |
407 | may wish to check the original repository for updates. | |
d19fbc3c | 408 | |
3c735e07 JM |
409 | The `git-fetch` command, with no arguments, will update all of the |
410 | remote-tracking branches to the latest version found in the original | |
d19fbc3c BF |
411 | repository. It will not touch any of your own branches--not even the |
412 | "master" branch that was created for you on clone. | |
413 | ||
e34caace | 414 | [[fetching-branches]] |
fd5b820d | 415 | === Fetching branches from other repositories |
d5cd5de4 BF |
416 | |
417 | You can also track branches from repositories other than the one you | |
5162e697 | 418 | cloned from, using linkgit:git-remote[1]: |
d5cd5de4 BF |
419 | |
420 | ------------------------------------------------- | |
34a25d4c TK |
421 | $ git remote add staging git://git.kernel.org/.../gregkh/staging.git |
422 | $ git fetch staging | |
423 | ... | |
424 | From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging | |
425 | * [new branch] master -> staging/master | |
426 | * [new branch] staging-linus -> staging/staging-linus | |
427 | * [new branch] staging-next -> staging/staging-next | |
d5cd5de4 BF |
428 | ------------------------------------------------- |
429 | ||
430 | New remote-tracking branches will be stored under the shorthand name | |
34a25d4c | 431 | that you gave `git remote add`, in this case `staging`: |
d5cd5de4 BF |
432 | |
433 | ------------------------------------------------- | |
434 | $ git branch -r | |
34a25d4c TK |
435 | origin/HEAD -> origin/master |
436 | origin/master | |
437 | staging/master | |
438 | staging/staging-linus | |
439 | staging/staging-next | |
d5cd5de4 BF |
440 | ------------------------------------------------- |
441 | ||
1249d8ad TK |
442 | If you run `git fetch <remote>` later, the remote-tracking branches |
443 | for the named `<remote>` will be updated. | |
d5cd5de4 | 444 | |
1249d8ad | 445 | If you examine the file `.git/config`, you will see that Git has added |
d5cd5de4 BF |
446 | a new stanza: |
447 | ||
448 | ------------------------------------------------- | |
449 | $ cat .git/config | |
450 | ... | |
34a25d4c TK |
451 | [remote "staging"] |
452 | url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git | |
453 | fetch = +refs/heads/*:refs/remotes/staging/* | |
d5cd5de4 BF |
454 | ... |
455 | ------------------------------------------------- | |
456 | ||
2de9b711 | 457 | This is what causes Git to track the remote's branches; you may modify |
1249d8ad | 458 | or delete these configuration options by editing `.git/config` with a |
fc90c536 | 459 | text editor. (See the "CONFIGURATION FILE" section of |
5162e697 | 460 | linkgit:git-config[1] for details.) |
d5cd5de4 | 461 | |
e34caace | 462 | [[exploring-git-history]] |
fd5b820d | 463 | == Exploring Git history |
d19fbc3c BF |
464 | |
465 | Git is best thought of as a tool for storing the history of a | |
466 | collection of files. It does this by storing compressed snapshots of | |
1130845b | 467 | the contents of a file hierarchy, together with "commits" which show |
d19fbc3c BF |
468 | the relationships between these snapshots. |
469 | ||
470 | Git provides extremely flexible and fast tools for exploring the | |
471 | history of a project. | |
472 | ||
aacd404e | 473 | We start with one specialized tool that is useful for finding the |
d19fbc3c BF |
474 | commit that introduced a bug into a project. |
475 | ||
e34caace | 476 | [[using-bisect]] |
fd5b820d | 477 | === How to use bisect to find a regression |
d19fbc3c BF |
478 | |
479 | Suppose version 2.6.18 of your project worked, but the version at | |
480 | "master" crashes. Sometimes the best way to find the cause of such a | |
481 | regression is to perform a brute-force search through the project's | |
482 | history to find the particular commit that caused the problem. The | |
5162e697 | 483 | linkgit:git-bisect[1] command can help you do this: |
d19fbc3c BF |
484 | |
485 | ------------------------------------------------- | |
486 | $ git bisect start | |
487 | $ git bisect good v2.6.18 | |
488 | $ git bisect bad master | |
489 | Bisecting: 3537 revisions left to test after this | |
490 | [65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6] | |
491 | ------------------------------------------------- | |
492 | ||
1249d8ad | 493 | If you run `git branch` at this point, you'll see that Git has |
0e25790f | 494 | temporarily moved you in "(no branch)". HEAD is now detached from any |
f61d89e1 | 495 | branch and points directly to a commit (with commit id 65934) that |
0e25790f CC |
496 | is reachable from "master" but not from v2.6.18. Compile and test it, |
497 | and see whether it crashes. Assume it does crash. Then: | |
d19fbc3c BF |
498 | |
499 | ------------------------------------------------- | |
500 | $ git bisect bad | |
501 | Bisecting: 1769 revisions left to test after this | |
502 | [7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings | |
503 | ------------------------------------------------- | |
504 | ||
2de9b711 | 505 | checks out an older version. Continue like this, telling Git at each |
d19fbc3c BF |
506 | stage whether the version it gives you is good or bad, and notice |
507 | that the number of revisions left to test is cut approximately in | |
508 | half each time. | |
509 | ||
510 | After about 13 tests (in this case), it will output the commit id of | |
511 | the guilty commit. You can then examine the commit with | |
5162e697 | 512 | linkgit:git-show[1], find out who wrote it, and mail them your bug |
d19fbc3c BF |
513 | report with the commit id. Finally, run |
514 | ||
515 | ------------------------------------------------- | |
516 | $ git bisect reset | |
517 | ------------------------------------------------- | |
518 | ||
0e25790f | 519 | to return you to the branch you were on before. |
d19fbc3c | 520 | |
6127c086 | 521 | Note that the version which `git bisect` checks out for you at each |
d19fbc3c BF |
522 | point is just a suggestion, and you're free to try a different |
523 | version if you think it would be a good idea. For example, | |
524 | occasionally you may land on a commit that broke something unrelated; | |
525 | run | |
526 | ||
527 | ------------------------------------------------- | |
04483524 | 528 | $ git bisect visualize |
d19fbc3c BF |
529 | ------------------------------------------------- |
530 | ||
531 | which will run gitk and label the commit it chose with a marker that | |
843c81dc | 532 | says "bisect". Choose a safe-looking commit nearby, note its commit |
d19fbc3c BF |
533 | id, and check it out with: |
534 | ||
535 | ------------------------------------------------- | |
f61d89e1 | 536 | $ git reset --hard fb47ddb2db |
d19fbc3c BF |
537 | ------------------------------------------------- |
538 | ||
1249d8ad | 539 | then test, run `bisect good` or `bisect bad` as appropriate, and |
d19fbc3c BF |
540 | continue. |
541 | ||
1249d8ad | 542 | Instead of `git bisect visualize` and then `git reset --hard |
f61d89e1 | 543 | fb47ddb2db`, you might just want to tell Git that you want to skip |
0e25790f CC |
544 | the current commit: |
545 | ||
546 | ------------------------------------------------- | |
547 | $ git bisect skip | |
548 | ------------------------------------------------- | |
549 | ||
2de9b711 | 550 | In this case, though, Git may not eventually be able to tell the first |
a0178ae2 | 551 | bad one between some first skipped commits and a later bad commit. |
0e25790f CC |
552 | |
553 | There are also ways to automate the bisecting process if you have a | |
554 | test script that can tell a good from a bad commit. See | |
1249d8ad TK |
555 | linkgit:git-bisect[1] for more information about this and other `git |
556 | bisect` features. | |
0e25790f | 557 | |
e34caace | 558 | [[naming-commits]] |
fd5b820d | 559 | === Naming commits |
d19fbc3c BF |
560 | |
561 | We have seen several ways of naming commits already: | |
562 | ||
d55ae921 | 563 | - 40-hexdigit object name |
d19fbc3c BF |
564 | - branch name: refers to the commit at the head of the given |
565 | branch | |
566 | - tag name: refers to the commit pointed to by the given tag | |
567 | (we've seen branches and tags are special cases of | |
568 | <<how-git-stores-references,references>>). | |
569 | - HEAD: refers to the head of the current branch | |
570 | ||
eb6ae7f4 | 571 | There are many more; see the "SPECIFYING REVISIONS" section of the |
9d83e382 | 572 | linkgit:gitrevisions[7] man page for the complete list of ways to |
d19fbc3c BF |
573 | name revisions. Some examples: |
574 | ||
575 | ------------------------------------------------- | |
d55ae921 | 576 | $ git show fb47ddb2 # the first few characters of the object name |
d19fbc3c BF |
577 | # are usually enough to specify it uniquely |
578 | $ git show HEAD^ # the parent of the HEAD commit | |
579 | $ git show HEAD^^ # the grandparent | |
580 | $ git show HEAD~4 # the great-great-grandparent | |
581 | ------------------------------------------------- | |
582 | ||
583 | Recall that merge commits may have more than one parent; by default, | |
1249d8ad | 584 | `^` and `~` follow the first parent listed in the commit, but you can |
d19fbc3c BF |
585 | also choose: |
586 | ||
587 | ------------------------------------------------- | |
588 | $ git show HEAD^1 # show the first parent of HEAD | |
589 | $ git show HEAD^2 # show the second parent of HEAD | |
590 | ------------------------------------------------- | |
591 | ||
592 | In addition to HEAD, there are several other special names for | |
593 | commits: | |
594 | ||
595 | Merges (to be discussed later), as well as operations such as | |
6127c086 | 596 | `git reset`, which change the currently checked-out commit, generally |
d19fbc3c BF |
597 | set ORIG_HEAD to the value HEAD had before the current operation. |
598 | ||
6127c086 FC |
599 | The `git fetch` operation always stores the head of the last fetched |
600 | branch in FETCH_HEAD. For example, if you run `git fetch` without | |
d19fbc3c BF |
601 | specifying a local branch as the target of the operation |
602 | ||
603 | ------------------------------------------------- | |
604 | $ git fetch git://example.com/proj.git theirbranch | |
605 | ------------------------------------------------- | |
606 | ||
607 | the fetched commits will still be available from FETCH_HEAD. | |
608 | ||
609 | When we discuss merges we'll also see the special name MERGE_HEAD, | |
610 | which refers to the other branch that we're merging in to the current | |
611 | branch. | |
612 | ||
5162e697 | 613 | The linkgit:git-rev-parse[1] command is a low-level command that is |
d55ae921 BF |
614 | occasionally useful for translating some name for a commit to the object |
615 | name for that commit: | |
aec053bb BF |
616 | |
617 | ------------------------------------------------- | |
618 | $ git rev-parse origin | |
619 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
620 | ------------------------------------------------- | |
621 | ||
e34caace | 622 | [[creating-tags]] |
fd5b820d | 623 | === Creating tags |
d19fbc3c BF |
624 | |
625 | We can also create a tag to refer to a particular commit; after | |
626 | running | |
627 | ||
628 | ------------------------------------------------- | |
04483524 | 629 | $ git tag stable-1 1b2e1d63ff |
d19fbc3c BF |
630 | ------------------------------------------------- |
631 | ||
1249d8ad | 632 | You can use `stable-1` to refer to the commit 1b2e1d63ff. |
d19fbc3c | 633 | |
c64415e2 BF |
634 | This creates a "lightweight" tag. If you would also like to include a |
635 | comment with the tag, and possibly sign it cryptographically, then you | |
5162e697 | 636 | should create a tag object instead; see the linkgit:git-tag[1] man page |
c64415e2 | 637 | for details. |
d19fbc3c | 638 | |
e34caace | 639 | [[browsing-revisions]] |
fd5b820d | 640 | === Browsing revisions |
d19fbc3c | 641 | |
5162e697 | 642 | The linkgit:git-log[1] command can show lists of commits. On its |
d19fbc3c BF |
643 | own, it shows all commits reachable from the parent commit; but you |
644 | can also make more specific requests: | |
645 | ||
646 | ------------------------------------------------- | |
647 | $ git log v2.5.. # commits since (not reachable from) v2.5 | |
648 | $ git log test..master # commits reachable from master but not test | |
649 | $ git log master..test # ...reachable from test but not master | |
650 | $ git log master...test # ...reachable from either test or master, | |
651 | # but not both | |
652 | $ git log --since="2 weeks ago" # commits from the last 2 weeks | |
653 | $ git log Makefile # commits which modify Makefile | |
654 | $ git log fs/ # ... which modify any file under fs/ | |
655 | $ git log -S'foo()' # commits which add or remove any file data | |
656 | # matching the string 'foo()' | |
657 | ------------------------------------------------- | |
658 | ||
659 | And of course you can combine all of these; the following finds | |
1249d8ad | 660 | commits since v2.5 which touch the `Makefile` or any file under `fs`: |
d19fbc3c BF |
661 | |
662 | ------------------------------------------------- | |
663 | $ git log v2.5.. Makefile fs/ | |
664 | ------------------------------------------------- | |
665 | ||
666 | You can also ask git log to show patches: | |
667 | ||
668 | ------------------------------------------------- | |
669 | $ git log -p | |
670 | ------------------------------------------------- | |
671 | ||
1249d8ad | 672 | See the `--pretty` option in the linkgit:git-log[1] man page for more |
d19fbc3c BF |
673 | display options. |
674 | ||
675 | Note that git log starts with the most recent commit and works | |
2de9b711 | 676 | backwards through the parents; however, since Git history can contain |
3dff5379 | 677 | multiple independent lines of development, the particular order that |
d19fbc3c BF |
678 | commits are listed in may be somewhat arbitrary. |
679 | ||
e34caace | 680 | [[generating-diffs]] |
fd5b820d | 681 | === Generating diffs |
d19fbc3c BF |
682 | |
683 | You can generate diffs between any two versions using | |
5162e697 | 684 | linkgit:git-diff[1]: |
d19fbc3c BF |
685 | |
686 | ------------------------------------------------- | |
687 | $ git diff master..test | |
688 | ------------------------------------------------- | |
689 | ||
5b98d9bc BF |
690 | That will produce the diff between the tips of the two branches. If |
691 | you'd prefer to find the diff from their common ancestor to test, you | |
692 | can use three dots instead of two: | |
693 | ||
694 | ------------------------------------------------- | |
695 | $ git diff master...test | |
696 | ------------------------------------------------- | |
697 | ||
698 | Sometimes what you want instead is a set of patches; for this you can | |
5162e697 | 699 | use linkgit:git-format-patch[1]: |
d19fbc3c BF |
700 | |
701 | ------------------------------------------------- | |
702 | $ git format-patch master..test | |
703 | ------------------------------------------------- | |
704 | ||
705 | will generate a file with a patch for each commit reachable from test | |
5b98d9bc | 706 | but not from master. |
d19fbc3c | 707 | |
e34caace | 708 | [[viewing-old-file-versions]] |
fd5b820d | 709 | === Viewing old file versions |
d19fbc3c BF |
710 | |
711 | You can always view an old version of a file by just checking out the | |
712 | correct revision first. But sometimes it is more convenient to be | |
713 | able to view an old version of a single file without checking | |
714 | anything out; this command does that: | |
715 | ||
716 | ------------------------------------------------- | |
717 | $ git show v2.5:fs/locks.c | |
718 | ------------------------------------------------- | |
719 | ||
720 | Before the colon may be anything that names a commit, and after it | |
2de9b711 | 721 | may be any path to a file tracked by Git. |
d19fbc3c | 722 | |
e34caace | 723 | [[history-examples]] |
fd5b820d | 724 | === Examples |
aec053bb | 725 | |
46acd3fa | 726 | [[counting-commits-on-a-branch]] |
fd5b820d | 727 | ==== Counting the number of commits on a branch |
46acd3fa | 728 | |
1249d8ad TK |
729 | Suppose you want to know how many commits you've made on `mybranch` |
730 | since it diverged from `origin`: | |
46acd3fa BF |
731 | |
732 | ------------------------------------------------- | |
733 | $ git log --pretty=oneline origin..mybranch | wc -l | |
734 | ------------------------------------------------- | |
735 | ||
736 | Alternatively, you may often see this sort of thing done with the | |
a6e5ef7d | 737 | lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's |
46acd3fa BF |
738 | of all the given commits: |
739 | ||
740 | ------------------------------------------------- | |
741 | $ git rev-list origin..mybranch | wc -l | |
742 | ------------------------------------------------- | |
743 | ||
e34caace | 744 | [[checking-for-equal-branches]] |
fd5b820d | 745 | ==== Check whether two branches point at the same history |
aec053bb BF |
746 | |
747 | Suppose you want to check whether two branches point at the same point | |
748 | in history. | |
749 | ||
750 | ------------------------------------------------- | |
751 | $ git diff origin..master | |
752 | ------------------------------------------------- | |
753 | ||
69f7ad73 BF |
754 | will tell you whether the contents of the project are the same at the |
755 | two branches; in theory, however, it's possible that the same project | |
756 | contents could have been arrived at by two different historical | |
d55ae921 | 757 | routes. You could compare the object names: |
aec053bb BF |
758 | |
759 | ------------------------------------------------- | |
760 | $ git rev-list origin | |
761 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
762 | $ git rev-list master | |
763 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
764 | ------------------------------------------------- | |
765 | ||
1249d8ad | 766 | Or you could recall that the `...` operator selects all commits |
ddd4ddef | 767 | reachable from either one reference or the other but not |
ddd2369c | 768 | both; so |
aec053bb BF |
769 | |
770 | ------------------------------------------------- | |
771 | $ git log origin...master | |
772 | ------------------------------------------------- | |
773 | ||
774 | will return no commits when the two branches are equal. | |
775 | ||
e34caace | 776 | [[finding-tagged-descendants]] |
fd5b820d | 777 | ==== Find first tagged version including a given fix |
aec053bb | 778 | |
69f7ad73 BF |
779 | Suppose you know that the commit e05db0fd fixed a certain problem. |
780 | You'd like to find the earliest tagged release that contains that | |
781 | fix. | |
782 | ||
783 | Of course, there may be more than one answer--if the history branched | |
784 | after commit e05db0fd, then there could be multiple "earliest" tagged | |
785 | releases. | |
786 | ||
787 | You could just visually inspect the commits since e05db0fd: | |
788 | ||
789 | ------------------------------------------------- | |
790 | $ gitk e05db0fd.. | |
791 | ------------------------------------------------- | |
792 | ||
ddd4ddef | 793 | or you can use linkgit:git-name-rev[1], which will give the commit a |
b181d57f BF |
794 | name based on any tag it finds pointing to one of the commit's |
795 | descendants: | |
796 | ||
797 | ------------------------------------------------- | |
04483524 | 798 | $ git name-rev --tags e05db0fd |
b181d57f BF |
799 | e05db0fd tags/v1.5.0-rc1^0~23 |
800 | ------------------------------------------------- | |
801 | ||
5162e697 | 802 | The linkgit:git-describe[1] command does the opposite, naming the |
b181d57f BF |
803 | revision using a tag on which the given commit is based: |
804 | ||
805 | ------------------------------------------------- | |
806 | $ git describe e05db0fd | |
04483524 | 807 | v1.5.0-rc0-260-ge05db0f |
b181d57f BF |
808 | ------------------------------------------------- |
809 | ||
810 | but that may sometimes help you guess which tags might come after the | |
811 | given commit. | |
812 | ||
813 | If you just want to verify whether a given tagged version contains a | |
5162e697 | 814 | given commit, you could use linkgit:git-merge-base[1]: |
b181d57f BF |
815 | |
816 | ------------------------------------------------- | |
817 | $ git merge-base e05db0fd v1.5.0-rc1 | |
818 | e05db0fd4f31dde7005f075a84f96b360d05984b | |
819 | ------------------------------------------------- | |
820 | ||
821 | The merge-base command finds a common ancestor of the given commits, | |
822 | and always returns one or the other in the case where one is a | |
823 | descendant of the other; so the above output shows that e05db0fd | |
824 | actually is an ancestor of v1.5.0-rc1. | |
825 | ||
826 | Alternatively, note that | |
827 | ||
828 | ------------------------------------------------- | |
4a7979ca | 829 | $ git log v1.5.0-rc1..e05db0fd |
b181d57f BF |
830 | ------------------------------------------------- |
831 | ||
4a7979ca | 832 | will produce empty output if and only if v1.5.0-rc1 includes e05db0fd, |
b181d57f | 833 | because it outputs only commits that are not reachable from v1.5.0-rc1. |
aec053bb | 834 | |
5162e697 | 835 | As yet another alternative, the linkgit:git-show-branch[1] command lists |
4a7979ca | 836 | the commits reachable from its arguments with a display on the left-hand |
ddd4ddef TA |
837 | side that indicates which arguments that commit is reachable from. |
838 | So, if you run something like | |
4a7979ca BF |
839 | |
840 | ------------------------------------------------- | |
841 | $ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2 | |
842 | ! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
843 | available | |
844 | ! [v1.5.0-rc0] GIT v1.5.0 preview | |
845 | ! [v1.5.0-rc1] GIT v1.5.0-rc1 | |
846 | ! [v1.5.0-rc2] GIT v1.5.0-rc2 | |
847 | ... | |
848 | ------------------------------------------------- | |
849 | ||
ddd4ddef | 850 | then a line like |
4a7979ca BF |
851 | |
852 | ------------------------------------------------- | |
853 | + ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
854 | available | |
855 | ------------------------------------------------- | |
856 | ||
ddd4ddef TA |
857 | shows that e05db0fd is reachable from itself, from v1.5.0-rc1, |
858 | and from v1.5.0-rc2, and not from v1.5.0-rc0. | |
4a7979ca | 859 | |
629d9f78 | 860 | [[showing-commits-unique-to-a-branch]] |
fd5b820d | 861 | ==== Showing commits unique to a given branch |
4a7979ca | 862 | |
629d9f78 | 863 | Suppose you would like to see all the commits reachable from the branch |
1249d8ad | 864 | head named `master` but not from any other head in your repository. |
d19fbc3c | 865 | |
629d9f78 | 866 | We can list all the heads in this repository with |
5162e697 | 867 | linkgit:git-show-ref[1]: |
d19fbc3c | 868 | |
629d9f78 BF |
869 | ------------------------------------------------- |
870 | $ git show-ref --heads | |
871 | bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial | |
872 | db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint | |
873 | a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master | |
874 | 24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2 | |
875 | 1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes | |
876 | ------------------------------------------------- | |
d19fbc3c | 877 | |
1249d8ad | 878 | We can get just the branch-head names, and remove `master`, with |
629d9f78 BF |
879 | the help of the standard utilities cut and grep: |
880 | ||
881 | ------------------------------------------------- | |
882 | $ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master' | |
883 | refs/heads/core-tutorial | |
884 | refs/heads/maint | |
885 | refs/heads/tutorial-2 | |
886 | refs/heads/tutorial-fixes | |
887 | ------------------------------------------------- | |
888 | ||
889 | And then we can ask to see all the commits reachable from master | |
890 | but not from these other heads: | |
891 | ||
892 | ------------------------------------------------- | |
893 | $ gitk master --not $( git show-ref --heads | cut -d' ' -f2 | | |
894 | grep -v '^refs/heads/master' ) | |
895 | ------------------------------------------------- | |
896 | ||
897 | Obviously, endless variations are possible; for example, to see all | |
898 | commits reachable from some head but not from any tag in the repository: | |
899 | ||
900 | ------------------------------------------------- | |
c78974f7 | 901 | $ gitk $( git show-ref --heads ) --not $( git show-ref --tags ) |
629d9f78 BF |
902 | ------------------------------------------------- |
903 | ||
9d83e382 | 904 | (See linkgit:gitrevisions[7] for explanations of commit-selecting |
629d9f78 BF |
905 | syntax such as `--not`.) |
906 | ||
82c8bf28 | 907 | [[making-a-release]] |
fd5b820d | 908 | ==== Creating a changelog and tarball for a software release |
82c8bf28 | 909 | |
5162e697 | 910 | The linkgit:git-archive[1] command can create a tar or zip archive from |
82c8bf28 BF |
911 | any version of a project; for example: |
912 | ||
913 | ------------------------------------------------- | |
7ed1690c | 914 | $ git archive -o latest.tar.gz --prefix=project/ HEAD |
82c8bf28 BF |
915 | ------------------------------------------------- |
916 | ||
7ed1690c TK |
917 | will use HEAD to produce a gzipped tar archive in which each filename |
918 | is preceded by `project/`. The output file format is inferred from | |
919 | the output file extension if possible, see linkgit:git-archive[1] for | |
920 | details. | |
921 | ||
1249d8ad | 922 | Versions of Git older than 1.7.7 don't know about the `tar.gz` format, |
7ed1690c TK |
923 | you'll need to use gzip explicitly: |
924 | ||
925 | ------------------------------------------------- | |
926 | $ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz | |
927 | ------------------------------------------------- | |
82c8bf28 BF |
928 | |
929 | If you're releasing a new version of a software project, you may want | |
930 | to simultaneously make a changelog to include in the release | |
931 | announcement. | |
932 | ||
933 | Linus Torvalds, for example, makes new kernel releases by tagging them, | |
934 | then running: | |
935 | ||
936 | ------------------------------------------------- | |
937 | $ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7 | |
938 | ------------------------------------------------- | |
939 | ||
940 | where release-script is a shell script that looks like: | |
941 | ||
942 | ------------------------------------------------- | |
943 | #!/bin/sh | |
944 | stable="$1" | |
945 | last="$2" | |
946 | new="$3" | |
947 | echo "# git tag v$new" | |
948 | echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz" | |
949 | echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz" | |
950 | echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new" | |
951 | echo "git shortlog --no-merges v$new ^v$last > ../ShortLog" | |
952 | echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new" | |
953 | ------------------------------------------------- | |
954 | ||
955 | and then he just cut-and-pastes the output commands after verifying that | |
956 | they look OK. | |
4a7979ca | 957 | |
e1ba4c32 | 958 | [[Finding-commits-With-given-Content]] |
fd5b820d | 959 | ==== Finding commits referencing a file with given content |
187b0d80 BF |
960 | |
961 | Somebody hands you a copy of a file, and asks which commits modified a | |
962 | file such that it contained the given content either before or after the | |
963 | commit. You can find out with this: | |
964 | ||
965 | ------------------------------------------------- | |
477ff5b7 | 966 | $ git log --raw --abbrev=40 --pretty=oneline | |
187b0d80 BF |
967 | grep -B 1 `git hash-object filename` |
968 | ------------------------------------------------- | |
969 | ||
970 | Figuring out why this works is left as an exercise to the (advanced) | |
5162e697 DM |
971 | student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and |
972 | linkgit:git-hash-object[1] man pages may prove helpful. | |
187b0d80 | 973 | |
aa971cb9 | 974 | [[Developing-With-git]] |
fd5b820d | 975 | == Developing with Git |
d19fbc3c | 976 | |
e34caace | 977 | [[telling-git-your-name]] |
fd5b820d | 978 | === Telling Git your name |
d19fbc3c | 979 | |
632cc3e6 TK |
980 | Before creating any commits, you should introduce yourself to Git. |
981 | The easiest way to do so is to use linkgit:git-config[1]: | |
982 | ||
983 | ------------------------------------------------ | |
984 | $ git config --global user.name 'Your Name Comes Here' | |
985 | $ git config --global user.email 'you@yourdomain.example.com' | |
986 | ------------------------------------------------ | |
987 | ||
988 | Which will add the following to a file named `.gitconfig` in your | |
989 | home directory: | |
d19fbc3c BF |
990 | |
991 | ------------------------------------------------ | |
d19fbc3c BF |
992 | [user] |
993 | name = Your Name Comes Here | |
994 | email = you@yourdomain.example.com | |
d19fbc3c BF |
995 | ------------------------------------------------ |
996 | ||
632cc3e6 TK |
997 | See the "CONFIGURATION FILE" section of linkgit:git-config[1] for |
998 | details on the configuration file. The file is plain text, so you can | |
999 | also edit it with your favorite editor. | |
fc90c536 | 1000 | |
d19fbc3c | 1001 | |
e34caace | 1002 | [[creating-a-new-repository]] |
fd5b820d | 1003 | === Creating a new repository |
d19fbc3c BF |
1004 | |
1005 | Creating a new repository from scratch is very easy: | |
1006 | ||
1007 | ------------------------------------------------- | |
1008 | $ mkdir project | |
1009 | $ cd project | |
f1d2b477 | 1010 | $ git init |
d19fbc3c BF |
1011 | ------------------------------------------------- |
1012 | ||
1013 | If you have some initial content (say, a tarball): | |
1014 | ||
1015 | ------------------------------------------------- | |
0ddd93b2 | 1016 | $ tar xzvf project.tar.gz |
d19fbc3c | 1017 | $ cd project |
f1d2b477 | 1018 | $ git init |
d19fbc3c BF |
1019 | $ git add . # include everything below ./ in the first commit: |
1020 | $ git commit | |
1021 | ------------------------------------------------- | |
1022 | ||
1023 | [[how-to-make-a-commit]] | |
fd5b820d | 1024 | === How to make a commit |
d19fbc3c BF |
1025 | |
1026 | Creating a new commit takes three steps: | |
1027 | ||
1028 | 1. Making some changes to the working directory using your | |
1029 | favorite editor. | |
2de9b711 TA |
1030 | 2. Telling Git about your changes. |
1031 | 3. Creating the commit using the content you told Git about | |
d19fbc3c BF |
1032 | in step 2. |
1033 | ||
1034 | In practice, you can interleave and repeat steps 1 and 2 as many | |
1035 | times as you want: in order to keep track of what you want committed | |
2de9b711 | 1036 | at step 3, Git maintains a snapshot of the tree's contents in a |
d19fbc3c BF |
1037 | special staging area called "the index." |
1038 | ||
01997b4a | 1039 | At the beginning, the content of the index will be identical to |
1249d8ad | 1040 | that of the HEAD. The command `git diff --cached`, which shows |
01997b4a BF |
1041 | the difference between the HEAD and the index, should therefore |
1042 | produce no output at that point. | |
eb6ae7f4 | 1043 | |
d19fbc3c BF |
1044 | Modifying the index is easy: |
1045 | ||
d39765b1 | 1046 | To update the index with the contents of a new or modified file, use |
d19fbc3c BF |
1047 | |
1048 | ------------------------------------------------- | |
1049 | $ git add path/to/file | |
1050 | ------------------------------------------------- | |
1051 | ||
d39765b1 | 1052 | To remove a file from the index and from the working tree, use |
d19fbc3c BF |
1053 | |
1054 | ------------------------------------------------- | |
1055 | $ git rm path/to/file | |
1056 | ------------------------------------------------- | |
1057 | ||
1058 | After each step you can verify that | |
1059 | ||
1060 | ------------------------------------------------- | |
1061 | $ git diff --cached | |
1062 | ------------------------------------------------- | |
1063 | ||
1064 | always shows the difference between the HEAD and the index file--this | |
1065 | is what you'd commit if you created the commit now--and that | |
1066 | ||
1067 | ------------------------------------------------- | |
1068 | $ git diff | |
1069 | ------------------------------------------------- | |
1070 | ||
1071 | shows the difference between the working tree and the index file. | |
1072 | ||
1249d8ad | 1073 | Note that `git add` always adds just the current contents of a file |
d19fbc3c | 1074 | to the index; further changes to the same file will be ignored unless |
6127c086 | 1075 | you run `git add` on the file again. |
d19fbc3c BF |
1076 | |
1077 | When you're ready, just run | |
1078 | ||
1079 | ------------------------------------------------- | |
1080 | $ git commit | |
1081 | ------------------------------------------------- | |
1082 | ||
2de9b711 | 1083 | and Git will prompt you for a commit message and then create the new |
3dff5379 | 1084 | commit. Check to make sure it looks like what you expected with |
d19fbc3c BF |
1085 | |
1086 | ------------------------------------------------- | |
1087 | $ git show | |
1088 | ------------------------------------------------- | |
1089 | ||
1090 | As a special shortcut, | |
a6080a0a | 1091 | |
d19fbc3c BF |
1092 | ------------------------------------------------- |
1093 | $ git commit -a | |
1094 | ------------------------------------------------- | |
1095 | ||
1096 | will update the index with any files that you've modified or removed | |
1097 | and create a commit, all in one step. | |
1098 | ||
1099 | A number of commands are useful for keeping track of what you're | |
1100 | about to commit: | |
1101 | ||
1102 | ------------------------------------------------- | |
1103 | $ git diff --cached # difference between HEAD and the index; what | |
1130845b | 1104 | # would be committed if you ran "commit" now. |
d19fbc3c BF |
1105 | $ git diff # difference between the index file and your |
1106 | # working directory; changes that would not | |
1107 | # be included if you ran "commit" now. | |
c64415e2 BF |
1108 | $ git diff HEAD # difference between HEAD and working tree; what |
1109 | # would be committed if you ran "commit -a" now. | |
d19fbc3c BF |
1110 | $ git status # a brief per-file summary of the above. |
1111 | ------------------------------------------------- | |
1112 | ||
5162e697 | 1113 | You can also use linkgit:git-gui[1] to create commits, view changes in |
407c0c87 BF |
1114 | the index and the working tree files, and individually select diff hunks |
1115 | for inclusion in the index (by right-clicking on the diff hunk and | |
1116 | choosing "Stage Hunk For Commit"). | |
1117 | ||
e34caace | 1118 | [[creating-good-commit-messages]] |
fd5b820d | 1119 | === Creating good commit messages |
d19fbc3c BF |
1120 | |
1121 | Though not required, it's a good idea to begin the commit message | |
1122 | with a single short (less than 50 character) line summarizing the | |
1123 | change, followed by a blank line and then a more thorough | |
52ffe995 JW |
1124 | description. The text up to the first blank line in a commit |
1125 | message is treated as the commit title, and that title is used | |
2de9b711 | 1126 | throughout Git. For example, linkgit:git-format-patch[1] turns a |
52ffe995 JW |
1127 | commit into email, and it uses the title on the Subject line and the |
1128 | rest of the commit in the body. | |
1129 | ||
d19fbc3c | 1130 | |
2dc53617 | 1131 | [[ignoring-files]] |
fd5b820d | 1132 | === Ignoring files |
2dc53617 | 1133 | |
2de9b711 | 1134 | A project will often generate files that you do 'not' want to track with Git. |
2dc53617 | 1135 | This typically includes files generated by a build process or temporary |
2de9b711 | 1136 | backup files made by your editor. Of course, 'not' tracking files with Git |
6127c086 | 1137 | is just a matter of 'not' calling `git add` on them. But it quickly becomes |
2dc53617 | 1138 | annoying to have these untracked files lying around; e.g. they make |
dcb11263 CJ |
1139 | `git add .` practically useless, and they keep showing up in the output of |
1140 | `git status`. | |
2dc53617 | 1141 | |
1249d8ad TK |
1142 | You can tell Git to ignore certain files by creating a file called |
1143 | `.gitignore` in the top level of your working directory, with contents | |
1144 | such as: | |
2dc53617 JH |
1145 | |
1146 | ------------------------------------------------- | |
1147 | # Lines starting with '#' are considered comments. | |
464a8a7a | 1148 | # Ignore any file named foo.txt. |
2dc53617 JH |
1149 | foo.txt |
1150 | # Ignore (generated) html files, | |
1151 | *.html | |
1152 | # except foo.html which is maintained by hand. | |
1153 | !foo.html | |
1154 | # Ignore objects and archives. | |
1155 | *.[oa] | |
1156 | ------------------------------------------------- | |
1157 | ||
5162e697 | 1158 | See linkgit:gitignore[5] for a detailed explanation of the syntax. You can |
464a8a7a BF |
1159 | also place .gitignore files in other directories in your working tree, and they |
1160 | will apply to those directories and their subdirectories. The `.gitignore` | |
1161 | files can be added to your repository like any other files (just run `git add | |
1162 | .gitignore` and `git commit`, as usual), which is convenient when the exclude | |
1163 | patterns (such as patterns matching build output files) would also make sense | |
1164 | for other users who clone your repository. | |
1165 | ||
1166 | If you wish the exclude patterns to affect only certain repositories | |
1167 | (instead of every repository for a given project), you may instead put | |
1249d8ad | 1168 | them in a file in your repository named `.git/info/exclude`, or in any |
da0005b8 | 1169 | file specified by the `core.excludesFile` configuration variable. |
1249d8ad TK |
1170 | Some Git commands can also take exclude patterns directly on the |
1171 | command line. See linkgit:gitignore[5] for the details. | |
2dc53617 | 1172 | |
e34caace | 1173 | [[how-to-merge]] |
fd5b820d | 1174 | === How to merge |
d19fbc3c BF |
1175 | |
1176 | You can rejoin two diverging branches of development using | |
5162e697 | 1177 | linkgit:git-merge[1]: |
d19fbc3c BF |
1178 | |
1179 | ------------------------------------------------- | |
1180 | $ git merge branchname | |
1181 | ------------------------------------------------- | |
1182 | ||
1249d8ad | 1183 | merges the development in the branch `branchname` into the current |
e63ec003 MM |
1184 | branch. |
1185 | ||
1249d8ad | 1186 | A merge is made by combining the changes made in `branchname` and the |
e63ec003 MM |
1187 | changes made up to the latest commit in your current branch since |
1188 | their histories forked. The work tree is overwritten by the result of | |
1189 | the merge when this combining is done cleanly, or overwritten by a | |
1190 | half-merged results when this combining results in conflicts. | |
1191 | Therefore, if you have uncommitted changes touching the same files as | |
1192 | the ones impacted by the merge, Git will refuse to proceed. Most of | |
1193 | the time, you will want to commit your changes before you can merge, | |
1194 | and if you don't, then linkgit:git-stash[1] can take these changes | |
1195 | away while you're doing the merge, and reapply them afterwards. | |
1196 | ||
6a5d0b0a | 1197 | If the changes are independent enough, Git will automatically complete |
e63ec003 MM |
1198 | the merge and commit the result (or reuse an existing commit in case |
1199 | of <<fast-forwards,fast-forward>>, see below). On the other hand, | |
1200 | if there are conflicts--for example, if the same file is | |
d19fbc3c BF |
1201 | modified in two different ways in the remote branch and the local |
1202 | branch--then you are warned; the output may look something like this: | |
1203 | ||
1204 | ------------------------------------------------- | |
fabbd8f6 BF |
1205 | $ git merge next |
1206 | 100% (4/4) done | |
1207 | Auto-merged file.txt | |
d19fbc3c BF |
1208 | CONFLICT (content): Merge conflict in file.txt |
1209 | Automatic merge failed; fix conflicts and then commit the result. | |
1210 | ------------------------------------------------- | |
1211 | ||
1212 | Conflict markers are left in the problematic files, and after | |
1213 | you resolve the conflicts manually, you can update the index | |
2de9b711 | 1214 | with the contents and run Git commit, as you normally would when |
d19fbc3c BF |
1215 | creating a new file. |
1216 | ||
1217 | If you examine the resulting commit using gitk, you will see that it | |
1218 | has two parents, one pointing to the top of the current branch, and | |
1219 | one to the top of the other branch. | |
1220 | ||
d19fbc3c | 1221 | [[resolving-a-merge]] |
fd5b820d | 1222 | === Resolving a merge |
d19fbc3c | 1223 | |
2de9b711 | 1224 | When a merge isn't resolved automatically, Git leaves the index and |
d19fbc3c BF |
1225 | the working tree in a special state that gives you all the |
1226 | information you need to help resolve the merge. | |
1227 | ||
1228 | Files with conflicts are marked specially in the index, so until you | |
5162e697 | 1229 | resolve the problem and update the index, linkgit:git-commit[1] will |
ef561ac7 | 1230 | fail: |
d19fbc3c BF |
1231 | |
1232 | ------------------------------------------------- | |
1233 | $ git commit | |
1234 | file.txt: needs merge | |
1235 | ------------------------------------------------- | |
1236 | ||
5162e697 | 1237 | Also, linkgit:git-status[1] will list those files as "unmerged", and the |
ef561ac7 BF |
1238 | files with conflicts will have conflict markers added, like this: |
1239 | ||
1240 | ------------------------------------------------- | |
1241 | <<<<<<< HEAD:file.txt | |
1242 | Hello world | |
1243 | ======= | |
1244 | Goodbye | |
1245 | >>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1246 | ------------------------------------------------- | |
1247 | ||
1248 | All you need to do is edit the files to resolve the conflicts, and then | |
1249 | ||
1250 | ------------------------------------------------- | |
1251 | $ git add file.txt | |
1252 | $ git commit | |
1253 | ------------------------------------------------- | |
1254 | ||
1255 | Note that the commit message will already be filled in for you with | |
1256 | some information about the merge. Normally you can just use this | |
1257 | default message unchanged, but you may add additional commentary of | |
1258 | your own if desired. | |
1259 | ||
2de9b711 | 1260 | The above is all you need to know to resolve a simple merge. But Git |
ef561ac7 BF |
1261 | also provides more information to help resolve conflicts: |
1262 | ||
e34caace | 1263 | [[conflict-resolution]] |
fd5b820d | 1264 | ==== Getting conflict-resolution help during a merge |
d19fbc3c | 1265 | |
2de9b711 | 1266 | All of the changes that Git was able to merge automatically are |
5162e697 | 1267 | already added to the index file, so linkgit:git-diff[1] shows only |
ef561ac7 | 1268 | the conflicts. It uses an unusual syntax: |
d19fbc3c BF |
1269 | |
1270 | ------------------------------------------------- | |
1271 | $ git diff | |
1272 | diff --cc file.txt | |
1273 | index 802992c,2b60207..0000000 | |
1274 | --- a/file.txt | |
1275 | +++ b/file.txt | |
1276 | @@@ -1,1 -1,1 +1,5 @@@ | |
1277 | ++<<<<<<< HEAD:file.txt | |
1278 | +Hello world | |
1279 | ++======= | |
1280 | + Goodbye | |
1281 | ++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
1282 | ------------------------------------------------- | |
1283 | ||
1130845b | 1284 | Recall that the commit which will be committed after we resolve this |
d19fbc3c BF |
1285 | conflict will have two parents instead of the usual one: one parent |
1286 | will be HEAD, the tip of the current branch; the other will be the | |
1287 | tip of the other branch, which is stored temporarily in MERGE_HEAD. | |
1288 | ||
ef561ac7 BF |
1289 | During the merge, the index holds three versions of each file. Each of |
1290 | these three "file stages" represents a different version of the file: | |
1291 | ||
1292 | ------------------------------------------------- | |
1293 | $ git show :1:file.txt # the file in a common ancestor of both branches | |
4209752d JH |
1294 | $ git show :2:file.txt # the version from HEAD. |
1295 | $ git show :3:file.txt # the version from MERGE_HEAD. | |
ef561ac7 BF |
1296 | ------------------------------------------------- |
1297 | ||
4209752d JH |
1298 | When you ask linkgit:git-diff[1] to show the conflicts, it runs a |
1299 | three-way diff between the conflicted merge results in the work tree with | |
1300 | stages 2 and 3 to show only hunks whose contents come from both sides, | |
1301 | mixed (in other words, when a hunk's merge results come only from stage 2, | |
1302 | that part is not conflicting and is not shown. Same for stage 3). | |
ef561ac7 BF |
1303 | |
1304 | The diff above shows the differences between the working-tree version of | |
1305 | file.txt and the stage 2 and stage 3 versions. So instead of preceding | |
1249d8ad | 1306 | each line by a single `+` or `-`, it now uses two columns: the first |
ef561ac7 BF |
1307 | column is used for differences between the first parent and the working |
1308 | directory copy, and the second for differences between the second parent | |
1309 | and the working directory copy. (See the "COMBINED DIFF FORMAT" section | |
5162e697 | 1310 | of linkgit:git-diff-files[1] for a details of the format.) |
ef561ac7 BF |
1311 | |
1312 | After resolving the conflict in the obvious way (but before updating the | |
1313 | index), the diff will look like: | |
d19fbc3c BF |
1314 | |
1315 | ------------------------------------------------- | |
1316 | $ git diff | |
1317 | diff --cc file.txt | |
1318 | index 802992c,2b60207..0000000 | |
1319 | --- a/file.txt | |
1320 | +++ b/file.txt | |
1321 | @@@ -1,1 -1,1 +1,1 @@@ | |
1322 | - Hello world | |
1323 | -Goodbye | |
1324 | ++Goodbye world | |
1325 | ------------------------------------------------- | |
1326 | ||
1327 | This shows that our resolved version deleted "Hello world" from the | |
1328 | first parent, deleted "Goodbye" from the second parent, and added | |
1329 | "Goodbye world", which was previously absent from both. | |
1330 | ||
ef561ac7 BF |
1331 | Some special diff options allow diffing the working directory against |
1332 | any of these stages: | |
1333 | ||
1334 | ------------------------------------------------- | |
1335 | $ git diff -1 file.txt # diff against stage 1 | |
1336 | $ git diff --base file.txt # same as the above | |
1337 | $ git diff -2 file.txt # diff against stage 2 | |
1338 | $ git diff --ours file.txt # same as the above | |
1339 | $ git diff -3 file.txt # diff against stage 3 | |
1340 | $ git diff --theirs file.txt # same as the above. | |
1341 | ------------------------------------------------- | |
1342 | ||
0cafe944 | 1343 | The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help |
ef561ac7 | 1344 | for merges: |
d19fbc3c BF |
1345 | |
1346 | ------------------------------------------------- | |
1347 | $ git log --merge | |
ef561ac7 | 1348 | $ gitk --merge |
d19fbc3c BF |
1349 | ------------------------------------------------- |
1350 | ||
ef561ac7 BF |
1351 | These will display all commits which exist only on HEAD or on |
1352 | MERGE_HEAD, and which touch an unmerged file. | |
d19fbc3c | 1353 | |
5162e697 | 1354 | You may also use linkgit:git-mergetool[1], which lets you merge the |
c7719fbe | 1355 | unmerged files using external tools such as Emacs or kdiff3. |
c64415e2 | 1356 | |
ef561ac7 | 1357 | Each time you resolve the conflicts in a file and update the index: |
d19fbc3c BF |
1358 | |
1359 | ------------------------------------------------- | |
1360 | $ git add file.txt | |
d19fbc3c BF |
1361 | ------------------------------------------------- |
1362 | ||
ef561ac7 | 1363 | the different stages of that file will be "collapsed", after which |
6127c086 | 1364 | `git diff` will (by default) no longer show diffs for that file. |
d19fbc3c BF |
1365 | |
1366 | [[undoing-a-merge]] | |
fd5b820d | 1367 | === Undoing a merge |
d19fbc3c BF |
1368 | |
1369 | If you get stuck and decide to just give up and throw the whole mess | |
1370 | away, you can always return to the pre-merge state with | |
1371 | ||
1372 | ------------------------------------------------- | |
fc991b43 | 1373 | $ git merge --abort |
d19fbc3c BF |
1374 | ------------------------------------------------- |
1375 | ||
1130845b | 1376 | Or, if you've already committed the merge that you want to throw away, |
d19fbc3c BF |
1377 | |
1378 | ------------------------------------------------- | |
1c73bb0e | 1379 | $ git reset --hard ORIG_HEAD |
d19fbc3c BF |
1380 | ------------------------------------------------- |
1381 | ||
1382 | However, this last command can be dangerous in some cases--never | |
1383 | throw away a commit you have already committed if that commit may | |
1384 | itself have been merged into another branch, as doing so may confuse | |
1385 | further merges. | |
1386 | ||
e34caace | 1387 | [[fast-forwards]] |
fd5b820d | 1388 | === Fast-forward merges |
d19fbc3c BF |
1389 | |
1390 | There is one special case not mentioned above, which is treated | |
1391 | differently. Normally, a merge results in a merge commit, with two | |
1392 | parents, one pointing at each of the two lines of development that | |
1393 | were merged. | |
1394 | ||
b2af4829 XF |
1395 | However, if the current branch is an ancestor of the other--so every commit |
1396 | present in the current branch is already contained in the other branch--then Git | |
1397 | just performs a "fast-forward"; the head of the current branch is moved forward | |
1398 | to point at the head of the merged-in branch, without any new commits being | |
1399 | created. | |
d19fbc3c | 1400 | |
e34caace | 1401 | [[fixing-mistakes]] |
fd5b820d | 1402 | === Fixing mistakes |
b684f830 BF |
1403 | |
1404 | If you've messed up the working tree, but haven't yet committed your | |
1405 | mistake, you can return the entire working tree to the last committed | |
1406 | state with | |
1407 | ||
1408 | ------------------------------------------------- | |
80f537f7 | 1409 | $ git restore --staged --worktree :/ |
b684f830 BF |
1410 | ------------------------------------------------- |
1411 | ||
1412 | If you make a commit that you later wish you hadn't, there are two | |
1413 | fundamentally different ways to fix the problem: | |
1414 | ||
1415 | 1. You can create a new commit that undoes whatever was done | |
93cbbd71 | 1416 | by the old commit. This is the correct thing if your |
b684f830 BF |
1417 | mistake has already been made public. |
1418 | ||
1419 | 2. You can go back and modify the old commit. You should | |
1420 | never do this if you have already made the history public; | |
2de9b711 | 1421 | Git does not normally expect the "history" of a project to |
b684f830 BF |
1422 | change, and cannot correctly perform repeated merges from |
1423 | a branch that has had its history changed. | |
1424 | ||
e34caace | 1425 | [[reverting-a-commit]] |
fd5b820d | 1426 | ==== Fixing a mistake with a new commit |
b684f830 BF |
1427 | |
1428 | Creating a new commit that reverts an earlier change is very easy; | |
5162e697 | 1429 | just pass the linkgit:git-revert[1] command a reference to the bad |
b684f830 BF |
1430 | commit; for example, to revert the most recent commit: |
1431 | ||
1432 | ------------------------------------------------- | |
1433 | $ git revert HEAD | |
1434 | ------------------------------------------------- | |
1435 | ||
1436 | This will create a new commit which undoes the change in HEAD. You | |
1437 | will be given a chance to edit the commit message for the new commit. | |
1438 | ||
1439 | You can also revert an earlier change, for example, the next-to-last: | |
1440 | ||
1441 | ------------------------------------------------- | |
1442 | $ git revert HEAD^ | |
1443 | ------------------------------------------------- | |
1444 | ||
2de9b711 | 1445 | In this case Git will attempt to undo the old change while leaving |
b684f830 BF |
1446 | intact any changes made since then. If more recent changes overlap |
1447 | with the changes to be reverted, then you will be asked to fix | |
1448 | conflicts manually, just as in the case of <<resolving-a-merge, | |
1449 | resolving a merge>>. | |
1450 | ||
7cb192ea | 1451 | [[fixing-a-mistake-by-rewriting-history]] |
fd5b820d | 1452 | ==== Fixing a mistake by rewriting history |
b684f830 BF |
1453 | |
1454 | If the problematic commit is the most recent commit, and you have not | |
1455 | yet made that commit public, then you may just | |
6127c086 | 1456 | <<undoing-a-merge,destroy it using `git reset`>>. |
b684f830 BF |
1457 | |
1458 | Alternatively, you | |
1459 | can edit the working directory and update the index to fix your | |
1460 | mistake, just as if you were going to <<how-to-make-a-commit,create a | |
1461 | new commit>>, then run | |
1462 | ||
1463 | ------------------------------------------------- | |
1464 | $ git commit --amend | |
1465 | ------------------------------------------------- | |
1466 | ||
1467 | which will replace the old commit by a new commit incorporating your | |
1468 | changes, giving you a chance to edit the old commit message first. | |
1469 | ||
1470 | Again, you should never do this to a commit that may already have | |
5162e697 | 1471 | been merged into another branch; use linkgit:git-revert[1] instead in |
b684f830 BF |
1472 | that case. |
1473 | ||
7cb192ea | 1474 | It is also possible to replace commits further back in the history, but |
b684f830 BF |
1475 | this is an advanced topic to be left for |
1476 | <<cleaning-up-history,another chapter>>. | |
1477 | ||
e34caace | 1478 | [[checkout-of-path]] |
fd5b820d | 1479 | ==== Checking out an old version of a file |
b684f830 BF |
1480 | |
1481 | In the process of undoing a previous bad change, you may find it | |
1482 | useful to check out an older version of a particular file using | |
80f537f7 | 1483 | linkgit:git-restore[1]. The command |
b684f830 BF |
1484 | |
1485 | ------------------------------------------------- | |
80f537f7 | 1486 | $ git restore --source=HEAD^ path/to/file |
b684f830 BF |
1487 | ------------------------------------------------- |
1488 | ||
1489 | replaces path/to/file by the contents it had in the commit HEAD^, and | |
1490 | also updates the index to match. It does not change branches. | |
1491 | ||
1492 | If you just want to look at an old version of the file, without | |
1493 | modifying the working directory, you can do that with | |
5162e697 | 1494 | linkgit:git-show[1]: |
b684f830 BF |
1495 | |
1496 | ------------------------------------------------- | |
ed4eb0d8 | 1497 | $ git show HEAD^:path/to/file |
b684f830 BF |
1498 | ------------------------------------------------- |
1499 | ||
1500 | which will display the given version of the file. | |
1501 | ||
7a7cc594 | 1502 | [[interrupted-work]] |
fd5b820d | 1503 | ==== Temporarily setting aside work in progress |
7a7cc594 JH |
1504 | |
1505 | While you are in the middle of working on something complicated, you | |
1506 | find an unrelated but obvious and trivial bug. You would like to fix it | |
5162e697 | 1507 | before continuing. You can use linkgit:git-stash[1] to save the current |
7a7cc594 JH |
1508 | state of your work, and after fixing the bug (or, optionally after doing |
1509 | so on a different branch and then coming back), unstash the | |
1510 | work-in-progress changes. | |
1511 | ||
1512 | ------------------------------------------------ | |
db37745e | 1513 | $ git stash push -m "work in progress for foo feature" |
7a7cc594 JH |
1514 | ------------------------------------------------ |
1515 | ||
1516 | This command will save your changes away to the `stash`, and | |
1517 | reset your working tree and the index to match the tip of your | |
1518 | current branch. Then you can make your fix as usual. | |
1519 | ||
1520 | ------------------------------------------------ | |
1521 | ... edit and test ... | |
1522 | $ git commit -a -m "blorpl: typofix" | |
1523 | ------------------------------------------------ | |
1524 | ||
1525 | After that, you can go back to what you were working on with | |
7b8988e1 | 1526 | `git stash pop`: |
7a7cc594 JH |
1527 | |
1528 | ------------------------------------------------ | |
7b8988e1 | 1529 | $ git stash pop |
7a7cc594 JH |
1530 | ------------------------------------------------ |
1531 | ||
1532 | ||
e34caace | 1533 | [[ensuring-good-performance]] |
fd5b820d | 1534 | === Ensuring good performance |
d19fbc3c | 1535 | |
2de9b711 | 1536 | On large repositories, Git depends on compression to keep the history |
901fd180 | 1537 | information from taking up too much space on disk or in memory. Some |
e1ebf212 | 1538 | Git commands may automatically run linkgit:git-gc[1], so you don't |
901fd180 TK |
1539 | have to worry about running it manually. However, compressing a large |
1540 | repository may take a while, so you may want to call `gc` explicitly | |
1541 | to avoid automatic compression kicking in when it is not convenient. | |
d19fbc3c | 1542 | |
e34caace BF |
1543 | |
1544 | [[ensuring-reliability]] | |
fd5b820d | 1545 | === Ensuring reliability |
11e016a3 | 1546 | |
e34caace | 1547 | [[checking-for-corruption]] |
fd5b820d | 1548 | ==== Checking the repository for corruption |
11e016a3 | 1549 | |
5162e697 | 1550 | The linkgit:git-fsck[1] command runs a number of self-consistency checks |
1191ee18 | 1551 | on the repository, and reports on any problems. This may take some |
c6a13b2c | 1552 | time. |
21dcb3b7 BF |
1553 | |
1554 | ------------------------------------------------- | |
04e50e94 | 1555 | $ git fsck |
21dcb3b7 BF |
1556 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 |
1557 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1558 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1559 | dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb | |
1560 | dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f | |
1561 | dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e | |
1562 | dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085 | |
1563 | dangling tree b24c2473f1fd3d91352a624795be026d64c8841f | |
1564 | ... | |
1565 | ------------------------------------------------- | |
1566 | ||
c6a13b2c JH |
1567 | You will see informational messages on dangling objects. They are objects |
1568 | that still exist in the repository but are no longer referenced by any of | |
1249d8ad | 1569 | your branches, and can (and will) be removed after a while with `gc`. |
b4ab1980 | 1570 | You can run `git fsck --no-dangling` to suppress these messages, and still |
c6a13b2c | 1571 | view real errors. |
1cdade2c | 1572 | |
e34caace | 1573 | [[recovering-lost-changes]] |
fd5b820d | 1574 | ==== Recovering lost changes |
11e016a3 | 1575 | |
e34caace | 1576 | [[reflogs]] |
fd5b820d | 1577 | ===== Reflogs |
559e4d7a | 1578 | |
1249d8ad TK |
1579 | Say you modify a branch with <<fixing-mistakes,`git reset --hard`>>, |
1580 | and then realize that the branch was the only reference you had to | |
1581 | that point in history. | |
559e4d7a | 1582 | |
2de9b711 | 1583 | Fortunately, Git also keeps a log, called a "reflog", of all the |
559e4d7a | 1584 | previous values of each branch. So in this case you can still find the |
a6080a0a | 1585 | old history using, for example, |
559e4d7a BF |
1586 | |
1587 | ------------------------------------------------- | |
1588 | $ git log master@{1} | |
1589 | ------------------------------------------------- | |
1590 | ||
e502c2c3 | 1591 | This lists the commits reachable from the previous version of the |
1249d8ad TK |
1592 | `master` branch head. This syntax can be used with any Git command |
1593 | that accepts a commit, not just with `git log`. Some other examples: | |
559e4d7a BF |
1594 | |
1595 | ------------------------------------------------- | |
1596 | $ git show master@{2} # See where the branch pointed 2, | |
1597 | $ git show master@{3} # 3, ... changes ago. | |
1598 | $ gitk master@{yesterday} # See where it pointed yesterday, | |
1599 | $ gitk master@{"1 week ago"} # ... or last week | |
953f3d6f BF |
1600 | $ git log --walk-reflogs master # show reflog entries for master |
1601 | ------------------------------------------------- | |
1602 | ||
1603 | A separate reflog is kept for the HEAD, so | |
1604 | ||
1605 | ------------------------------------------------- | |
1606 | $ git show HEAD@{"1 week ago"} | |
559e4d7a BF |
1607 | ------------------------------------------------- |
1608 | ||
953f3d6f BF |
1609 | will show what HEAD pointed to one week ago, not what the current branch |
1610 | pointed to one week ago. This allows you to see the history of what | |
1611 | you've checked out. | |
1612 | ||
559e4d7a | 1613 | The reflogs are kept by default for 30 days, after which they may be |
5162e697 | 1614 | pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn |
559e4d7a | 1615 | how to control this pruning, and see the "SPECIFYING REVISIONS" |
9d83e382 | 1616 | section of linkgit:gitrevisions[7] for details. |
559e4d7a | 1617 | |
2de9b711 | 1618 | Note that the reflog history is very different from normal Git history. |
559e4d7a BF |
1619 | While normal history is shared by every repository that works on the |
1620 | same project, the reflog history is not shared: it tells you only about | |
1621 | how the branches in your local repository have changed over time. | |
1622 | ||
59723040 | 1623 | [[dangling-object-recovery]] |
fd5b820d | 1624 | ===== Examining dangling objects |
559e4d7a | 1625 | |
59723040 BF |
1626 | In some situations the reflog may not be able to save you. For example, |
1627 | suppose you delete a branch, then realize you need the history it | |
1628 | contained. The reflog is also deleted; however, if you have not yet | |
1629 | pruned the repository, then you may still be able to find the lost | |
6127c086 | 1630 | commits in the dangling objects that `git fsck` reports. See |
59723040 | 1631 | <<dangling-objects>> for the details. |
559e4d7a BF |
1632 | |
1633 | ------------------------------------------------- | |
1634 | $ git fsck | |
1635 | dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 | |
1636 | dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
1637 | dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
1638 | ... | |
1639 | ------------------------------------------------- | |
1640 | ||
aacd404e | 1641 | You can examine |
559e4d7a BF |
1642 | one of those dangling commits with, for example, |
1643 | ||
1644 | ------------------------------------------------ | |
1645 | $ gitk 7281251ddd --not --all | |
1646 | ------------------------------------------------ | |
1647 | ||
1648 | which does what it sounds like: it says that you want to see the commit | |
1649 | history that is described by the dangling commit(s), but not the | |
1650 | history that is described by all your existing branches and tags. Thus | |
1651 | you get exactly the history reachable from that commit that is lost. | |
1652 | (And notice that it might not be just one commit: we only report the | |
1653 | "tip of the line" as being dangling, but there might be a whole deep | |
79c96c57 | 1654 | and complex commit history that was dropped.) |
559e4d7a BF |
1655 | |
1656 | If you decide you want the history back, you can always create a new | |
1657 | reference pointing to it, for example, a new branch: | |
1658 | ||
1659 | ------------------------------------------------ | |
a6080a0a | 1660 | $ git branch recovered-branch 7281251ddd |
559e4d7a BF |
1661 | ------------------------------------------------ |
1662 | ||
59723040 BF |
1663 | Other types of dangling objects (blobs and trees) are also possible, and |
1664 | dangling objects can arise in other situations. | |
1665 | ||
11e016a3 | 1666 | |
e34caace | 1667 | [[sharing-development]] |
fd5b820d | 1668 | == Sharing development with others |
d19fbc3c | 1669 | |
aa971cb9 | 1670 | [[getting-updates-With-git-pull]] |
fd5b820d | 1671 | === Getting updates with git pull |
d19fbc3c | 1672 | |
e63ec003 | 1673 | After you clone a repository and commit a few changes of your own, you |
d19fbc3c BF |
1674 | may wish to check the original repository for updates and merge them |
1675 | into your own work. | |
1676 | ||
aa971cb9 | 1677 | We have already seen <<Updating-a-repository-With-git-fetch,how to |
0e615b25 | 1678 | keep remote-tracking branches up to date>> with linkgit:git-fetch[1], |
d19fbc3c BF |
1679 | and how to merge two branches. So you can merge in changes from the |
1680 | original repository's master branch with: | |
1681 | ||
1682 | ------------------------------------------------- | |
1683 | $ git fetch | |
1684 | $ git merge origin/master | |
1685 | ------------------------------------------------- | |
1686 | ||
5162e697 | 1687 | However, the linkgit:git-pull[1] command provides a way to do this in |
d19fbc3c BF |
1688 | one step: |
1689 | ||
1690 | ------------------------------------------------- | |
1691 | $ git pull origin master | |
1692 | ------------------------------------------------- | |
1693 | ||
1249d8ad TK |
1694 | In fact, if you have `master` checked out, then this branch has been |
1695 | configured by `git clone` to get changes from the HEAD branch of the | |
66a062a1 | 1696 | origin repository. So often you can |
0eb4f7cd | 1697 | accomplish the above with just a simple |
d19fbc3c BF |
1698 | |
1699 | ------------------------------------------------- | |
1700 | $ git pull | |
1701 | ------------------------------------------------- | |
1702 | ||
66a062a1 MM |
1703 | This command will fetch changes from the remote branches to your |
1704 | remote-tracking branches `origin/*`, and merge the default branch into | |
1705 | the current branch. | |
1706 | ||
29b9a66f MM |
1707 | More generally, a branch that is created from a remote-tracking branch |
1708 | will pull | |
0eb4f7cd | 1709 | by default from that branch. See the descriptions of the |
1249d8ad | 1710 | `branch.<name>.remote` and `branch.<name>.merge` options in |
5162e697 DM |
1711 | linkgit:git-config[1], and the discussion of the `--track` option in |
1712 | linkgit:git-checkout[1], to learn how to control these defaults. | |
d19fbc3c | 1713 | |
1249d8ad | 1714 | In addition to saving you keystrokes, `git pull` also helps you by |
d19fbc3c BF |
1715 | producing a default commit message documenting the branch and |
1716 | repository that you pulled from. | |
1717 | ||
1718 | (But note that no such commit will be created in the case of a | |
a75d7b54 | 1719 | <<fast-forwards,fast-forward>>; instead, your branch will just be |
79c96c57 | 1720 | updated to point to the latest commit from the upstream branch.) |
d19fbc3c | 1721 | |
1249d8ad | 1722 | The `git pull` command can also be given `.` as the "remote" repository, |
1191ee18 | 1723 | in which case it just merges in a branch from the current repository; so |
4c63ff45 BF |
1724 | the commands |
1725 | ||
1726 | ------------------------------------------------- | |
1727 | $ git pull . branch | |
1728 | $ git merge branch | |
1729 | ------------------------------------------------- | |
1730 | ||
a7bdee11 | 1731 | are roughly equivalent. |
4c63ff45 | 1732 | |
e34caace | 1733 | [[submitting-patches]] |
fd5b820d | 1734 | === Submitting patches to a project |
d19fbc3c BF |
1735 | |
1736 | If you just have a few changes, the simplest way to submit them may | |
1737 | just be to send them as patches in email: | |
1738 | ||
5162e697 | 1739 | First, use linkgit:git-format-patch[1]; for example: |
d19fbc3c BF |
1740 | |
1741 | ------------------------------------------------- | |
eb6ae7f4 | 1742 | $ git format-patch origin |
d19fbc3c BF |
1743 | ------------------------------------------------- |
1744 | ||
1745 | will produce a numbered series of files in the current directory, one | |
1249d8ad | 1746 | for each patch in the current branch but not in `origin/HEAD`. |
d19fbc3c | 1747 | |
d84cef18 PO |
1748 | `git format-patch` can include an initial "cover letter". You can insert |
1749 | commentary on individual patches after the three dash line which | |
1750 | `format-patch` places after the commit message but before the patch | |
1751 | itself. If you use `git notes` to track your cover letter material, | |
1752 | `git format-patch --notes` will include the commit's notes in a similar | |
1753 | manner. | |
1754 | ||
d19fbc3c BF |
1755 | You can then import these into your mail client and send them by |
1756 | hand. However, if you have a lot to send at once, you may prefer to | |
5162e697 | 1757 | use the linkgit:git-send-email[1] script to automate the process. |
3c735e07 JM |
1758 | Consult the mailing list for your project first to determine |
1759 | their requirements for submitting patches. | |
d19fbc3c | 1760 | |
e34caace | 1761 | [[importing-patches]] |
fd5b820d | 1762 | === Importing patches to a project |
d19fbc3c | 1763 | |
5162e697 | 1764 | Git also provides a tool called linkgit:git-am[1] (am stands for |
d19fbc3c BF |
1765 | "apply mailbox"), for importing such an emailed series of patches. |
1766 | Just save all of the patch-containing messages, in order, into a | |
1249d8ad | 1767 | single mailbox file, say `patches.mbox`, then run |
d19fbc3c BF |
1768 | |
1769 | ------------------------------------------------- | |
eb6ae7f4 | 1770 | $ git am -3 patches.mbox |
d19fbc3c BF |
1771 | ------------------------------------------------- |
1772 | ||
1773 | Git will apply each patch in order; if any conflicts are found, it | |
1774 | will stop, and you can fix the conflicts as described in | |
1249d8ad | 1775 | "<<resolving-a-merge,Resolving a merge>>". (The `-3` option tells |
2de9b711 | 1776 | Git to perform a merge; if you would prefer it just to abort and |
01997b4a BF |
1777 | leave your tree and index untouched, you may omit that option.) |
1778 | ||
1779 | Once the index is updated with the results of the conflict | |
1780 | resolution, instead of creating a new commit, just run | |
d19fbc3c BF |
1781 | |
1782 | ------------------------------------------------- | |
8ceb6fbd | 1783 | $ git am --continue |
d19fbc3c BF |
1784 | ------------------------------------------------- |
1785 | ||
2de9b711 | 1786 | and Git will create the commit for you and continue applying the |
d19fbc3c BF |
1787 | remaining patches from the mailbox. |
1788 | ||
1789 | The final result will be a series of commits, one for each patch in | |
1790 | the original mailbox, with authorship and commit log message each | |
1791 | taken from the message containing each patch. | |
1792 | ||
eda69449 | 1793 | [[public-repositories]] |
fd5b820d | 1794 | === Public Git repositories |
d19fbc3c | 1795 | |
6e30fb0c DK |
1796 | Another way to submit changes to a project is to tell the maintainer |
1797 | of that project to pull the changes from your repository using | |
aa971cb9 | 1798 | linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull, |
6127c086 | 1799 | Getting updates with `git pull`>>" we described this as a way to get |
6e30fb0c DK |
1800 | updates from the "main" repository, but it works just as well in the |
1801 | other direction. | |
d19fbc3c | 1802 | |
eda69449 BF |
1803 | If you and the maintainer both have accounts on the same machine, then |
1804 | you can just pull changes from each other's repositories directly; | |
11d51533 | 1805 | commands that accept repository URLs as arguments will also accept a |
eda69449 | 1806 | local directory name: |
d19fbc3c BF |
1807 | |
1808 | ------------------------------------------------- | |
1809 | $ git clone /path/to/repository | |
1810 | $ git pull /path/to/other/repository | |
1811 | ------------------------------------------------- | |
1812 | ||
c9016158 | 1813 | or an ssh URL: |
11d51533 BF |
1814 | |
1815 | ------------------------------------------------- | |
1816 | $ git clone ssh://yourhost/~you/repository | |
1817 | ------------------------------------------------- | |
1818 | ||
1819 | For projects with few developers, or for synchronizing a few private | |
1820 | repositories, this may be all you need. | |
1821 | ||
eda69449 BF |
1822 | However, the more common way to do this is to maintain a separate public |
1823 | repository (usually on a different host) for others to pull changes | |
1824 | from. This is usually more convenient, and allows you to cleanly | |
1825 | separate private work in progress from publicly visible work. | |
d19fbc3c BF |
1826 | |
1827 | You will continue to do your day-to-day work in your personal | |
1828 | repository, but periodically "push" changes from your personal | |
1829 | repository into your public repository, allowing other developers to | |
1830 | pull from that repository. So the flow of changes, in a situation | |
1831 | where there is one other developer with a public repository, looks | |
1832 | like this: | |
1833 | ||
c4d2f614 MÅ |
1834 | .... |
1835 | you push | |
1836 | your personal repo ------------------> your public repo | |
1837 | ^ | | |
1838 | | | | |
1839 | | you pull | they pull | |
1840 | | | | |
1841 | | | | |
1842 | | they push V | |
1843 | their public repo <------------------- their repo | |
1844 | .... | |
d19fbc3c | 1845 | |
11d51533 BF |
1846 | We explain how to do this in the following sections. |
1847 | ||
eda69449 | 1848 | [[setting-up-a-public-repository]] |
fd5b820d | 1849 | ==== Setting up a public repository |
eda69449 | 1850 | |
1249d8ad | 1851 | Assume your personal repository is in the directory `~/proj`. We |
6127c086 | 1852 | first create a new clone of the repository and tell `git daemon` that it |
eda69449 | 1853 | is meant to be public: |
d19fbc3c BF |
1854 | |
1855 | ------------------------------------------------- | |
52c80037 | 1856 | $ git clone --bare ~/proj proj.git |
eda69449 | 1857 | $ touch proj.git/git-daemon-export-ok |
d19fbc3c BF |
1858 | ------------------------------------------------- |
1859 | ||
52c80037 | 1860 | The resulting directory proj.git contains a "bare" git repository--it is |
1249d8ad | 1861 | just the contents of the `.git` directory, without any files checked out |
eda69449 | 1862 | around it. |
d19fbc3c | 1863 | |
1249d8ad | 1864 | Next, copy `proj.git` to the server where you plan to host the |
d19fbc3c BF |
1865 | public repository. You can use scp, rsync, or whatever is most |
1866 | convenient. | |
1867 | ||
eda69449 | 1868 | [[exporting-via-git]] |
fd5b820d | 1869 | ==== Exporting a Git repository via the Git protocol |
eda69449 BF |
1870 | |
1871 | This is the preferred method. | |
1872 | ||
1873 | If someone else administers the server, they should tell you what | |
1249d8ad TK |
1874 | directory to put the repository in, and what `git://` URL it will |
1875 | appear at. You can then skip to the section | |
d19fbc3c BF |
1876 | "<<pushing-changes-to-a-public-repository,Pushing changes to a public |
1877 | repository>>", below. | |
1878 | ||
5162e697 | 1879 | Otherwise, all you need to do is start linkgit:git-daemon[1]; it will |
eda69449 | 1880 | listen on port 9418. By default, it will allow access to any directory |
2de9b711 | 1881 | that looks like a Git directory and contains the magic file |
6127c086 | 1882 | git-daemon-export-ok. Passing some directory paths as `git daemon` |
eda69449 BF |
1883 | arguments will further restrict the exports to those paths. |
1884 | ||
6127c086 | 1885 | You can also run `git daemon` as an inetd service; see the |
5162e697 | 1886 | linkgit:git-daemon[1] man page for details. (See especially the |
eda69449 | 1887 | examples section.) |
d19fbc3c BF |
1888 | |
1889 | [[exporting-via-http]] | |
fd5b820d | 1890 | ==== Exporting a git repository via HTTP |
d19fbc3c | 1891 | |
2de9b711 | 1892 | The Git protocol gives better performance and reliability, but on a |
de3f2c7b | 1893 | host with a web server set up, HTTP exports may be simpler to set up. |
d19fbc3c | 1894 | |
2de9b711 | 1895 | All you need to do is place the newly created bare Git repository in |
d19fbc3c BF |
1896 | a directory that is exported by the web server, and make some |
1897 | adjustments to give web clients some extra information they need: | |
1898 | ||
1899 | ------------------------------------------------- | |
1900 | $ mv proj.git /home/you/public_html/proj.git | |
1901 | $ cd proj.git | |
c64415e2 | 1902 | $ git --bare update-server-info |
7dce9918 | 1903 | $ mv hooks/post-update.sample hooks/post-update |
d19fbc3c BF |
1904 | ------------------------------------------------- |
1905 | ||
1906 | (For an explanation of the last two lines, see | |
6998e4db | 1907 | linkgit:git-update-server-info[1] and linkgit:githooks[5].) |
d19fbc3c | 1908 | |
1249d8ad | 1909 | Advertise the URL of `proj.git`. Anybody else should then be able to |
c9016158 | 1910 | clone or pull from that URL, for example with a command line like: |
d19fbc3c BF |
1911 | |
1912 | ------------------------------------------------- | |
1913 | $ git clone http://yourserver.com/~you/proj.git | |
1914 | ------------------------------------------------- | |
1915 | ||
1916 | (See also | |
d5ff3b4b | 1917 | link:howto/setup-git-server-over-http.html[setup-git-server-over-http] |
d19fbc3c | 1918 | for a slightly more sophisticated setup using WebDAV which also |
de3f2c7b | 1919 | allows pushing over HTTP.) |
d19fbc3c | 1920 | |
d19fbc3c | 1921 | [[pushing-changes-to-a-public-repository]] |
fd5b820d | 1922 | ==== Pushing changes to a public repository |
d19fbc3c | 1923 | |
eda69449 | 1924 | Note that the two techniques outlined above (exporting via |
d19fbc3c BF |
1925 | <<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other |
1926 | maintainers to fetch your latest changes, but they do not allow write | |
1927 | access, which you will need to update the public repository with the | |
1928 | latest changes created in your private repository. | |
1929 | ||
5162e697 | 1930 | The simplest way to do this is using linkgit:git-push[1] and ssh; to |
1249d8ad TK |
1931 | update the remote branch named `master` with the latest state of your |
1932 | branch named `master`, run | |
d19fbc3c BF |
1933 | |
1934 | ------------------------------------------------- | |
1935 | $ git push ssh://yourserver.com/~you/proj.git master:master | |
1936 | ------------------------------------------------- | |
1937 | ||
1938 | or just | |
1939 | ||
1940 | ------------------------------------------------- | |
1941 | $ git push ssh://yourserver.com/~you/proj.git master | |
1942 | ------------------------------------------------- | |
1943 | ||
6127c086 | 1944 | As with `git fetch`, `git push` will complain if this does not result in a |
a75d7b54 | 1945 | <<fast-forwards,fast-forward>>; see the following section for details on |
81eb417a | 1946 | handling this case. |
d19fbc3c | 1947 | |
1249d8ad | 1948 | Note that the target of a `push` is normally a |
11d51533 | 1949 | <<def_bare_repository,bare>> repository. You can also push to a |
d9be2485 TK |
1950 | repository that has a checked-out working tree, but a push to update the |
1951 | currently checked-out branch is denied by default to prevent confusion. | |
50995edd | 1952 | See the description of the receive.denyCurrentBranch option |
d9be2485 | 1953 | in linkgit:git-config[1] for details. |
11d51533 | 1954 | |
6127c086 | 1955 | As with `git fetch`, you may also set up configuration options to |
e9b49083 TK |
1956 | save typing; so, for example: |
1957 | ||
1958 | ------------------------------------------------- | |
1959 | $ git remote add public-repo ssh://yourserver.com/~you/proj.git | |
1960 | ------------------------------------------------- | |
1961 | ||
1962 | adds the following to `.git/config`: | |
d19fbc3c BF |
1963 | |
1964 | ------------------------------------------------- | |
d19fbc3c | 1965 | [remote "public-repo"] |
e9b49083 TK |
1966 | url = yourserver.com:proj.git |
1967 | fetch = +refs/heads/*:refs/remotes/example/* | |
d19fbc3c BF |
1968 | ------------------------------------------------- |
1969 | ||
e9b49083 | 1970 | which lets you do the same push with just |
d19fbc3c BF |
1971 | |
1972 | ------------------------------------------------- | |
1973 | $ git push public-repo master | |
1974 | ------------------------------------------------- | |
1975 | ||
1249d8ad TK |
1976 | See the explanations of the `remote.<name>.url`, |
1977 | `branch.<name>.remote`, and `remote.<name>.push` options in | |
1978 | linkgit:git-config[1] for details. | |
d19fbc3c | 1979 | |
81eb417a | 1980 | [[forcing-push]] |
fd5b820d | 1981 | ==== What to do when a push fails |
81eb417a | 1982 | |
a75d7b54 | 1983 | If a push would not result in a <<fast-forwards,fast-forward>> of the |
81eb417a BF |
1984 | remote branch, then it will fail with an error like: |
1985 | ||
1986 | ------------------------------------------------- | |
3c82eec8 MÅ |
1987 | ! [rejected] master -> master (non-fast-forward) |
1988 | error: failed to push some refs to '...' | |
1989 | hint: Updates were rejected because the tip of your current branch is behind | |
1990 | hint: its remote counterpart. Integrate the remote changes (e.g. | |
1991 | hint: 'git pull ...') before pushing again. | |
1992 | hint: See the 'Note about fast-forwards' in 'git push --help' for details. | |
81eb417a BF |
1993 | ------------------------------------------------- |
1994 | ||
1995 | This can happen, for example, if you: | |
1996 | ||
6127c086 FC |
1997 | - use `git reset --hard` to remove already-published commits, or |
1998 | - use `git commit --amend` to replace already-published commits | |
7cb192ea | 1999 | (as in <<fixing-a-mistake-by-rewriting-history>>), or |
6127c086 | 2000 | - use `git rebase` to rebase any already-published commits (as |
81eb417a BF |
2001 | in <<using-git-rebase>>). |
2002 | ||
6127c086 | 2003 | You may force `git push` to perform the update anyway by preceding the |
81eb417a BF |
2004 | branch name with a plus sign: |
2005 | ||
2006 | ------------------------------------------------- | |
2007 | $ git push ssh://yourserver.com/~you/proj.git +master | |
2008 | ------------------------------------------------- | |
2009 | ||
d1471e06 TK |
2010 | Note the addition of the `+` sign. Alternatively, you can use the |
2011 | `-f` flag to force the remote update, as in: | |
2012 | ||
2013 | ------------------------------------------------- | |
2014 | $ git push -f ssh://yourserver.com/~you/proj.git master | |
2015 | ------------------------------------------------- | |
2016 | ||
81eb417a | 2017 | Normally whenever a branch head in a public repository is modified, it |
9e5d87d4 | 2018 | is modified to point to a descendant of the commit that it pointed to |
81eb417a | 2019 | before. By forcing a push in this situation, you break that convention. |
aa971cb9 | 2020 | (See <<problems-With-rewriting-history>>.) |
81eb417a BF |
2021 | |
2022 | Nevertheless, this is a common practice for people that need a simple | |
2023 | way to publish a work-in-progress patch series, and it is an acceptable | |
2024 | compromise as long as you warn other developers that this is how you | |
2025 | intend to manage the branch. | |
2026 | ||
2027 | It's also possible for a push to fail in this way when other people have | |
2028 | the right to push to the same repository. In that case, the correct | |
843c81dc EH |
2029 | solution is to retry the push after first updating your work: either by a |
2030 | pull, or by a fetch followed by a rebase; see the | |
81eb417a | 2031 | <<setting-up-a-shared-repository,next section>> and |
6998e4db | 2032 | linkgit:gitcvs-migration[7] for more. |
81eb417a | 2033 | |
e34caace | 2034 | [[setting-up-a-shared-repository]] |
fd5b820d | 2035 | ==== Setting up a shared repository |
d19fbc3c BF |
2036 | |
2037 | Another way to collaborate is by using a model similar to that | |
2038 | commonly used in CVS, where several developers with special rights | |
2039 | all push to and pull from a single shared repository. See | |
6998e4db | 2040 | linkgit:gitcvs-migration[7] for instructions on how to |
d19fbc3c BF |
2041 | set this up. |
2042 | ||
2de9b711 | 2043 | However, while there is nothing wrong with Git's support for shared |
8fae2225 | 2044 | repositories, this mode of operation is not generally recommended, |
2de9b711 | 2045 | simply because the mode of collaboration that Git supports--by |
8fae2225 BF |
2046 | exchanging patches and pulling from public repositories--has so many |
2047 | advantages over the central shared repository: | |
2048 | ||
2049 | - Git's ability to quickly import and merge patches allows a | |
2050 | single maintainer to process incoming changes even at very | |
6127c086 | 2051 | high rates. And when that becomes too much, `git pull` provides |
8fae2225 BF |
2052 | an easy way for that maintainer to delegate this job to other |
2053 | maintainers while still allowing optional review of incoming | |
2054 | changes. | |
2055 | - Since every developer's repository has the same complete copy | |
2056 | of the project history, no repository is special, and it is | |
2057 | trivial for another developer to take over maintenance of a | |
2058 | project, either by mutual agreement, or because a maintainer | |
2059 | becomes unresponsive or difficult to work with. | |
2060 | - The lack of a central group of "committers" means there is | |
2061 | less need for formal decisions about who is "in" and who is | |
2062 | "out". | |
2063 | ||
e34caace | 2064 | [[setting-up-gitweb]] |
fd5b820d | 2065 | ==== Allowing web browsing of a repository |
d19fbc3c | 2066 | |
a8cd1402 | 2067 | The gitweb cgi script provides users an easy way to browse your |
99487cf2 SS |
2068 | project's revisions, file contents and logs without having to install |
2069 | Git. Features like RSS/Atom feeds and blame/annotation details may | |
2070 | optionally be enabled. | |
2071 | ||
2072 | The linkgit:git-instaweb[1] command provides a simple way to start | |
2073 | browsing the repository using gitweb. The default server when using | |
2074 | instaweb is lighttpd. | |
2075 | ||
2076 | See the file gitweb/INSTALL in the Git source tree and | |
d285ab0a | 2077 | linkgit:gitweb[1] for instructions on details setting up a permanent |
99487cf2 | 2078 | installation with a CGI or Perl capable server. |
d19fbc3c | 2079 | |
9cfde9ee | 2080 | [[how-to-get-a-git-repository-with-minimal-history]] |
fd5b820d | 2081 | === How to get a Git repository with minimal history |
9cfde9ee SS |
2082 | |
2083 | A <<def_shallow_clone,shallow clone>>, with its truncated | |
2084 | history, is useful when one is interested only in recent history | |
2085 | of a project and getting full history from the upstream is | |
2086 | expensive. | |
2087 | ||
2088 | A <<def_shallow_clone,shallow clone>> is created by specifying | |
2089 | the linkgit:git-clone[1] `--depth` switch. The depth can later be | |
2090 | changed with the linkgit:git-fetch[1] `--depth` switch, or full | |
2091 | history restored with `--unshallow`. | |
2092 | ||
2093 | Merging inside a <<def_shallow_clone,shallow clone>> will work as long | |
2094 | as a merge base is in the recent history. | |
2095 | Otherwise, it will be like merging unrelated histories and may | |
2096 | have to result in huge conflicts. This limitation may make such | |
2097 | a repository unsuitable to be used in merge based workflows. | |
d19fbc3c | 2098 | |
e34caace | 2099 | [[sharing-development-examples]] |
fd5b820d | 2100 | === Examples |
d19fbc3c | 2101 | |
9e2163ea | 2102 | [[maintaining-topic-branches]] |
fd5b820d | 2103 | ==== Maintaining topic branches for a Linux subsystem maintainer |
9e2163ea | 2104 | |
2de9b711 | 2105 | This describes how Tony Luck uses Git in his role as maintainer of the |
9e2163ea BF |
2106 | IA64 architecture for the Linux kernel. |
2107 | ||
2108 | He uses two public branches: | |
2109 | ||
2110 | - A "test" tree into which patches are initially placed so that they | |
2111 | can get some exposure when integrated with other ongoing development. | |
2112 | This tree is available to Andrew for pulling into -mm whenever he | |
2113 | wants. | |
2114 | ||
2115 | - A "release" tree into which tested patches are moved for final sanity | |
2116 | checking, and as a vehicle to send them upstream to Linus (by sending | |
2117 | him a "please pull" request.) | |
2118 | ||
2119 | He also uses a set of temporary branches ("topic branches"), each | |
2120 | containing a logical grouping of patches. | |
2121 | ||
2122 | To set this up, first create your work tree by cloning Linus's public | |
2123 | tree: | |
2124 | ||
2125 | ------------------------------------------------- | |
283efb01 | 2126 | $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work |
9e2163ea BF |
2127 | $ cd work |
2128 | ------------------------------------------------- | |
2129 | ||
29b9a66f | 2130 | Linus's tree will be stored in the remote-tracking branch named origin/master, |
5162e697 DM |
2131 | and can be updated using linkgit:git-fetch[1]; you can track other |
2132 | public trees using linkgit:git-remote[1] to set up a "remote" and | |
7560f547 | 2133 | linkgit:git-fetch[1] to keep them up to date; see |
6e30fb0c | 2134 | <<repositories-and-branches>>. |
9e2163ea BF |
2135 | |
2136 | Now create the branches in which you are going to work; these start out | |
2137 | at the current tip of origin/master branch, and should be set up (using | |
1249d8ad | 2138 | the `--track` option to linkgit:git-branch[1]) to merge changes in from |
9e2163ea BF |
2139 | Linus by default. |
2140 | ||
2141 | ------------------------------------------------- | |
2142 | $ git branch --track test origin/master | |
2143 | $ git branch --track release origin/master | |
2144 | ------------------------------------------------- | |
2145 | ||
5162e697 | 2146 | These can be easily kept up to date using linkgit:git-pull[1]. |
9e2163ea BF |
2147 | |
2148 | ------------------------------------------------- | |
328c6cb8 NTND |
2149 | $ git switch test && git pull |
2150 | $ git switch release && git pull | |
9e2163ea BF |
2151 | ------------------------------------------------- |
2152 | ||
2153 | Important note! If you have any local changes in these branches, then | |
2154 | this merge will create a commit object in the history (with no local | |
2de9b711 | 2155 | changes Git will simply do a "fast-forward" merge). Many people dislike |
9e2163ea | 2156 | the "noise" that this creates in the Linux history, so you should avoid |
1249d8ad | 2157 | doing this capriciously in the `release` branch, as these noisy commits |
9e2163ea BF |
2158 | will become part of the permanent history when you ask Linus to pull |
2159 | from the release branch. | |
2160 | ||
5162e697 | 2161 | A few configuration variables (see linkgit:git-config[1]) can |
9e2163ea BF |
2162 | make it easy to push both branches to your public tree. (See |
2163 | <<setting-up-a-public-repository>>.) | |
2164 | ||
2165 | ------------------------------------------------- | |
2166 | $ cat >> .git/config <<EOF | |
2167 | [remote "mytree"] | |
283efb01 | 2168 | url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git |
9e2163ea BF |
2169 | push = release |
2170 | push = test | |
2171 | EOF | |
2172 | ------------------------------------------------- | |
2173 | ||
2174 | Then you can push both the test and release trees using | |
5162e697 | 2175 | linkgit:git-push[1]: |
9e2163ea BF |
2176 | |
2177 | ------------------------------------------------- | |
2178 | $ git push mytree | |
2179 | ------------------------------------------------- | |
2180 | ||
2181 | or push just one of the test and release branches using: | |
2182 | ||
2183 | ------------------------------------------------- | |
2184 | $ git push mytree test | |
2185 | ------------------------------------------------- | |
2186 | ||
2187 | or | |
2188 | ||
2189 | ------------------------------------------------- | |
2190 | $ git push mytree release | |
2191 | ------------------------------------------------- | |
2192 | ||
2193 | Now to apply some patches from the community. Think of a short | |
2194 | snappy name for a branch to hold this patch (or related group of | |
352953a5 TL |
2195 | patches), and create a new branch from a recent stable tag of |
2196 | Linus's branch. Picking a stable base for your branch will: | |
2197 | 1) help you: by avoiding inclusion of unrelated and perhaps lightly | |
2198 | tested changes | |
1249d8ad | 2199 | 2) help future bug hunters that use `git bisect` to find problems |
9e2163ea BF |
2200 | |
2201 | ------------------------------------------------- | |
328c6cb8 | 2202 | $ git switch -c speed-up-spinlocks v2.6.35 |
9e2163ea BF |
2203 | ------------------------------------------------- |
2204 | ||
2205 | Now you apply the patch(es), run some tests, and commit the change(s). If | |
2206 | the patch is a multi-part series, then you should apply each as a separate | |
2207 | commit to this branch. | |
2208 | ||
2209 | ------------------------------------------------- | |
2210 | $ ... patch ... test ... commit [ ... patch ... test ... commit ]* | |
2211 | ------------------------------------------------- | |
2212 | ||
a7bdee11 | 2213 | When you are happy with the state of this change, you can merge it into the |
9e2163ea BF |
2214 | "test" branch in preparation to make it public: |
2215 | ||
2216 | ------------------------------------------------- | |
328c6cb8 | 2217 | $ git switch test && git merge speed-up-spinlocks |
9e2163ea BF |
2218 | ------------------------------------------------- |
2219 | ||
2220 | It is unlikely that you would have any conflicts here ... but you might if you | |
2221 | spent a while on this step and had also pulled new versions from upstream. | |
2222 | ||
3c735e07 | 2223 | Sometime later when enough time has passed and testing done, you can pull the |
1249d8ad | 2224 | same branch into the `release` tree ready to go upstream. This is where you |
9e2163ea | 2225 | see the value of keeping each patch (or patch series) in its own branch. It |
1249d8ad | 2226 | means that the patches can be moved into the `release` tree in any order. |
9e2163ea BF |
2227 | |
2228 | ------------------------------------------------- | |
328c6cb8 | 2229 | $ git switch release && git merge speed-up-spinlocks |
9e2163ea BF |
2230 | ------------------------------------------------- |
2231 | ||
2232 | After a while, you will have a number of branches, and despite the | |
2233 | well chosen names you picked for each of them, you may forget what | |
2234 | they are for, or what status they are in. To get a reminder of what | |
2235 | changes are in a specific branch, use: | |
2236 | ||
2237 | ------------------------------------------------- | |
467c0197 | 2238 | $ git log linux..branchname | git shortlog |
9e2163ea BF |
2239 | ------------------------------------------------- |
2240 | ||
06ada152 | 2241 | To see whether it has already been merged into the test or release branches, |
9e2163ea BF |
2242 | use: |
2243 | ||
2244 | ------------------------------------------------- | |
2245 | $ git log test..branchname | |
2246 | ------------------------------------------------- | |
2247 | ||
2248 | or | |
2249 | ||
2250 | ------------------------------------------------- | |
2251 | $ git log release..branchname | |
2252 | ------------------------------------------------- | |
2253 | ||
06ada152 | 2254 | (If this branch has not yet been merged, you will see some log entries. |
9e2163ea BF |
2255 | If it has been merged, then there will be no output.) |
2256 | ||
2257 | Once a patch completes the great cycle (moving from test to release, | |
2258 | then pulled by Linus, and finally coming back into your local | |
1249d8ad | 2259 | `origin/master` branch), the branch for this change is no longer needed. |
9e2163ea BF |
2260 | You detect this when the output from: |
2261 | ||
2262 | ------------------------------------------------- | |
2263 | $ git log origin..branchname | |
2264 | ------------------------------------------------- | |
2265 | ||
2266 | is empty. At this point the branch can be deleted: | |
2267 | ||
2268 | ------------------------------------------------- | |
2269 | $ git branch -d branchname | |
2270 | ------------------------------------------------- | |
2271 | ||
2272 | Some changes are so trivial that it is not necessary to create a separate | |
2273 | branch and then merge into each of the test and release branches. For | |
1249d8ad TK |
2274 | these changes, just apply directly to the `release` branch, and then |
2275 | merge that into the `test` branch. | |
9e2163ea | 2276 | |
ae6ef554 TK |
2277 | After pushing your work to `mytree`, you can use |
2278 | linkgit:git-request-pull[1] to prepare a "please pull" request message | |
2279 | to send to Linus: | |
9e2163ea BF |
2280 | |
2281 | ------------------------------------------------- | |
ae6ef554 TK |
2282 | $ git push mytree |
2283 | $ git request-pull origin mytree release | |
9e2163ea BF |
2284 | ------------------------------------------------- |
2285 | ||
2286 | Here are some of the scripts that simplify all this even further. | |
2287 | ||
2288 | ------------------------------------------------- | |
2289 | ==== update script ==== | |
48a8c26c | 2290 | # Update a branch in my Git tree. If the branch to be updated |
9e2163ea BF |
2291 | # is origin, then pull from kernel.org. Otherwise merge |
2292 | # origin/master branch into test|release branch | |
2293 | ||
2294 | case "$1" in | |
2295 | test|release) | |
2296 | git checkout $1 && git pull . origin | |
2297 | ;; | |
2298 | origin) | |
fc74ecc1 | 2299 | before=$(git rev-parse refs/remotes/origin/master) |
9e2163ea | 2300 | git fetch origin |
fc74ecc1 | 2301 | after=$(git rev-parse refs/remotes/origin/master) |
9e2163ea BF |
2302 | if [ $before != $after ] |
2303 | then | |
2304 | git log $before..$after | git shortlog | |
2305 | fi | |
2306 | ;; | |
2307 | *) | |
1a2ba8b9 | 2308 | echo "usage: $0 origin|test|release" 1>&2 |
9e2163ea BF |
2309 | exit 1 |
2310 | ;; | |
2311 | esac | |
2312 | ------------------------------------------------- | |
2313 | ||
2314 | ------------------------------------------------- | |
2315 | ==== merge script ==== | |
2316 | # Merge a branch into either the test or release branch | |
2317 | ||
2318 | pname=$0 | |
2319 | ||
2320 | usage() | |
2321 | { | |
1a2ba8b9 | 2322 | echo "usage: $pname branch test|release" 1>&2 |
9e2163ea BF |
2323 | exit 1 |
2324 | } | |
2325 | ||
fc74ecc1 | 2326 | git show-ref -q --verify -- refs/heads/"$1" || { |
9e2163ea BF |
2327 | echo "Can't see branch <$1>" 1>&2 |
2328 | usage | |
fc74ecc1 | 2329 | } |
9e2163ea BF |
2330 | |
2331 | case "$2" in | |
2332 | test|release) | |
2333 | if [ $(git log $2..$1 | wc -c) -eq 0 ] | |
2334 | then | |
2335 | echo $1 already merged into $2 1>&2 | |
2336 | exit 1 | |
2337 | fi | |
2338 | git checkout $2 && git pull . $1 | |
2339 | ;; | |
2340 | *) | |
2341 | usage | |
2342 | ;; | |
2343 | esac | |
2344 | ------------------------------------------------- | |
2345 | ||
2346 | ------------------------------------------------- | |
2347 | ==== status script ==== | |
48a8c26c | 2348 | # report on status of my ia64 Git tree |
9e2163ea BF |
2349 | |
2350 | gb=$(tput setab 2) | |
2351 | rb=$(tput setab 1) | |
2352 | restore=$(tput setab 9) | |
2353 | ||
2354 | if [ `git rev-list test..release | wc -c` -gt 0 ] | |
2355 | then | |
2356 | echo $rb Warning: commits in release that are not in test $restore | |
2357 | git log test..release | |
2358 | fi | |
2359 | ||
fc74ecc1 | 2360 | for branch in `git show-ref --heads | sed 's|^.*/||'` |
9e2163ea BF |
2361 | do |
2362 | if [ $branch = test -o $branch = release ] | |
2363 | then | |
2364 | continue | |
2365 | fi | |
2366 | ||
2367 | echo -n $gb ======= $branch ====== $restore " " | |
2368 | status= | |
2369 | for ref in test release origin/master | |
2370 | do | |
2371 | if [ `git rev-list $ref..$branch | wc -c` -gt 0 ] | |
2372 | then | |
2373 | status=$status${ref:0:1} | |
2374 | fi | |
2375 | done | |
2376 | case $status in | |
2377 | trl) | |
2378 | echo $rb Need to pull into test $restore | |
2379 | ;; | |
2380 | rl) | |
2381 | echo "In test" | |
2382 | ;; | |
2383 | l) | |
2384 | echo "Waiting for linus" | |
2385 | ;; | |
2386 | "") | |
2387 | echo $rb All done $restore | |
2388 | ;; | |
2389 | *) | |
2390 | echo $rb "<$status>" $restore | |
2391 | ;; | |
2392 | esac | |
2393 | git log origin/master..$branch | git shortlog | |
2394 | done | |
2395 | ------------------------------------------------- | |
d19fbc3c | 2396 | |
d19fbc3c | 2397 | |
d19fbc3c | 2398 | [[cleaning-up-history]] |
fd5b820d | 2399 | == Rewriting history and maintaining patch series |
4c63ff45 BF |
2400 | |
2401 | Normally commits are only added to a project, never taken away or | |
2402 | replaced. Git is designed with this assumption, and violating it will | |
2de9b711 | 2403 | cause Git's merge machinery (for example) to do the wrong thing. |
4c63ff45 BF |
2404 | |
2405 | However, there is a situation in which it can be useful to violate this | |
2406 | assumption. | |
2407 | ||
e34caace | 2408 | [[patch-series]] |
fd5b820d | 2409 | === Creating the perfect patch series |
4c63ff45 BF |
2410 | |
2411 | Suppose you are a contributor to a large project, and you want to add a | |
2412 | complicated feature, and to present it to the other developers in a way | |
2413 | that makes it easy for them to read your changes, verify that they are | |
2414 | correct, and understand why you made each change. | |
2415 | ||
b181d57f | 2416 | If you present all of your changes as a single patch (or commit), they |
79c96c57 | 2417 | may find that it is too much to digest all at once. |
4c63ff45 BF |
2418 | |
2419 | If you present them with the entire history of your work, complete with | |
2420 | mistakes, corrections, and dead ends, they may be overwhelmed. | |
2421 | ||
2422 | So the ideal is usually to produce a series of patches such that: | |
2423 | ||
2424 | 1. Each patch can be applied in order. | |
2425 | ||
2426 | 2. Each patch includes a single logical change, together with a | |
2427 | message explaining the change. | |
2428 | ||
2429 | 3. No patch introduces a regression: after applying any initial | |
2430 | part of the series, the resulting project still compiles and | |
2431 | works, and has no bugs that it didn't have before. | |
2432 | ||
2433 | 4. The complete series produces the same end result as your own | |
2434 | (probably much messier!) development process did. | |
2435 | ||
b181d57f BF |
2436 | We will introduce some tools that can help you do this, explain how to |
2437 | use them, and then explain some of the problems that can arise because | |
2438 | you are rewriting history. | |
4c63ff45 | 2439 | |
e34caace | 2440 | [[using-git-rebase]] |
fd5b820d | 2441 | === Keeping a patch series up to date using git rebase |
4c63ff45 | 2442 | |
1249d8ad TK |
2443 | Suppose that you create a branch `mywork` on a remote-tracking branch |
2444 | `origin`, and create some commits on top of it: | |
4c63ff45 BF |
2445 | |
2446 | ------------------------------------------------- | |
328c6cb8 | 2447 | $ git switch -c mywork origin |
4c63ff45 BF |
2448 | $ vi file.txt |
2449 | $ git commit | |
2450 | $ vi otherfile.txt | |
2451 | $ git commit | |
2452 | ... | |
2453 | ------------------------------------------------- | |
2454 | ||
2455 | You have performed no merges into mywork, so it is just a simple linear | |
1249d8ad | 2456 | sequence of patches on top of `origin`: |
4c63ff45 | 2457 | |
1dc71a91 | 2458 | ................................................ |
fa8347b8 | 2459 | o--o--O <-- origin |
4c63ff45 | 2460 | \ |
fa8347b8 | 2461 | a--b--c <-- mywork |
1dc71a91 | 2462 | ................................................ |
4c63ff45 BF |
2463 | |
2464 | Some more interesting work has been done in the upstream project, and | |
1249d8ad | 2465 | `origin` has advanced: |
4c63ff45 | 2466 | |
1dc71a91 | 2467 | ................................................ |
4c63ff45 BF |
2468 | o--o--O--o--o--o <-- origin |
2469 | \ | |
2470 | a--b--c <-- mywork | |
1dc71a91 | 2471 | ................................................ |
4c63ff45 | 2472 | |
1249d8ad | 2473 | At this point, you could use `pull` to merge your changes back in; |
4c63ff45 BF |
2474 | the result would create a new merge commit, like this: |
2475 | ||
1dc71a91 | 2476 | ................................................ |
4c63ff45 BF |
2477 | o--o--O--o--o--o <-- origin |
2478 | \ \ | |
2479 | a--b--c--m <-- mywork | |
1dc71a91 | 2480 | ................................................ |
a6080a0a | 2481 | |
4c63ff45 BF |
2482 | However, if you prefer to keep the history in mywork a simple series of |
2483 | commits without any merges, you may instead choose to use | |
5162e697 | 2484 | linkgit:git-rebase[1]: |
4c63ff45 BF |
2485 | |
2486 | ------------------------------------------------- | |
328c6cb8 | 2487 | $ git switch mywork |
4c63ff45 BF |
2488 | $ git rebase origin |
2489 | ------------------------------------------------- | |
2490 | ||
b181d57f | 2491 | This will remove each of your commits from mywork, temporarily saving |
1249d8ad | 2492 | them as patches (in a directory named `.git/rebase-apply`), update mywork to |
b181d57f BF |
2493 | point at the latest version of origin, then apply each of the saved |
2494 | patches to the new mywork. The result will look like: | |
4c63ff45 BF |
2495 | |
2496 | ||
1dc71a91 | 2497 | ................................................ |
4c63ff45 BF |
2498 | o--o--O--o--o--o <-- origin |
2499 | \ | |
2500 | a'--b'--c' <-- mywork | |
1dc71a91 | 2501 | ................................................ |
4c63ff45 | 2502 | |
b181d57f | 2503 | In the process, it may discover conflicts. In that case it will stop |
6127c086 | 2504 | and allow you to fix the conflicts; after fixing conflicts, use `git add` |
7a7d4ef6 | 2505 | to update the index with those contents, and then, instead of |
6127c086 | 2506 | running `git commit`, just run |
4c63ff45 BF |
2507 | |
2508 | ------------------------------------------------- | |
2509 | $ git rebase --continue | |
2510 | ------------------------------------------------- | |
2511 | ||
2de9b711 | 2512 | and Git will continue applying the rest of the patches. |
4c63ff45 | 2513 | |
b6cbca38 | 2514 | At any point you may use the `--abort` option to abort this process and |
4c63ff45 BF |
2515 | return mywork to the state it had before you started the rebase: |
2516 | ||
2517 | ------------------------------------------------- | |
2518 | $ git rebase --abort | |
2519 | ------------------------------------------------- | |
2520 | ||
6c26bf4d TK |
2521 | If you need to reorder or edit a number of commits in a branch, it may |
2522 | be easier to use `git rebase -i`, which allows you to reorder and | |
2523 | squash commits, as well as marking them for individual editing during | |
2524 | the rebase. See <<interactive-rebase>> for details, and | |
2525 | <<reordering-patch-series>> for alternatives. | |
2526 | ||
7cb192ea | 2527 | [[rewriting-one-commit]] |
fd5b820d | 2528 | === Rewriting a single commit |
365aa199 | 2529 | |
7cb192ea | 2530 | We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the |
365aa199 BF |
2531 | most recent commit using |
2532 | ||
2533 | ------------------------------------------------- | |
2534 | $ git commit --amend | |
2535 | ------------------------------------------------- | |
2536 | ||
2537 | which will replace the old commit by a new commit incorporating your | |
2538 | changes, giving you a chance to edit the old commit message first. | |
6c26bf4d TK |
2539 | This is useful for fixing typos in your last commit, or for adjusting |
2540 | the patch contents of a poorly staged commit. | |
365aa199 | 2541 | |
6c26bf4d TK |
2542 | If you need to amend commits from deeper in your history, you can |
2543 | use <<interactive-rebase,interactive rebase's `edit` instruction>>. | |
365aa199 | 2544 | |
6c26bf4d | 2545 | [[reordering-patch-series]] |
fd5b820d | 2546 | === Reordering or selecting from a patch series |
365aa199 | 2547 | |
6c26bf4d TK |
2548 | Sometimes you want to edit a commit deeper in your history. One |
2549 | approach is to use `git format-patch` to create a series of patches | |
2550 | and then reset the state to before the patches: | |
365aa199 BF |
2551 | |
2552 | ------------------------------------------------- | |
6c26bf4d TK |
2553 | $ git format-patch origin |
2554 | $ git reset --hard origin | |
365aa199 BF |
2555 | ------------------------------------------------- |
2556 | ||
6c26bf4d TK |
2557 | Then modify, reorder, or eliminate patches as needed before applying |
2558 | them again with linkgit:git-am[1]: | |
365aa199 BF |
2559 | |
2560 | ------------------------------------------------- | |
6c26bf4d | 2561 | $ git am *.patch |
365aa199 BF |
2562 | ------------------------------------------------- |
2563 | ||
6c26bf4d | 2564 | [[interactive-rebase]] |
fd5b820d | 2565 | === Using interactive rebases |
365aa199 | 2566 | |
6c26bf4d TK |
2567 | You can also edit a patch series with an interactive rebase. This is |
2568 | the same as <<reordering-patch-series,reordering a patch series using | |
2569 | `format-patch`>>, so use whichever interface you like best. | |
4c63ff45 | 2570 | |
6c26bf4d TK |
2571 | Rebase your current HEAD on the last commit you want to retain as-is. |
2572 | For example, if you want to reorder the last 5 commits, use: | |
b181d57f BF |
2573 | |
2574 | ------------------------------------------------- | |
6c26bf4d | 2575 | $ git rebase -i HEAD~5 |
b181d57f BF |
2576 | ------------------------------------------------- |
2577 | ||
6c26bf4d TK |
2578 | This will open your editor with a list of steps to be taken to perform |
2579 | your rebase. | |
4c63ff45 | 2580 | |
b181d57f | 2581 | ------------------------------------------------- |
6c26bf4d TK |
2582 | pick deadbee The oneline of this commit |
2583 | pick fa1afe1 The oneline of the next commit | |
2584 | ... | |
4c63ff45 | 2585 | |
6c26bf4d TK |
2586 | # Rebase c0ffeee..deadbee onto c0ffeee |
2587 | # | |
2588 | # Commands: | |
2589 | # p, pick = use commit | |
2590 | # r, reword = use commit, but edit the commit message | |
2591 | # e, edit = use commit, but stop for amending | |
2592 | # s, squash = use commit, but meld into previous commit | |
2593 | # f, fixup = like "squash", but discard this commit's log message | |
2594 | # x, exec = run command (the rest of the line) using shell | |
2595 | # | |
2596 | # These lines can be re-ordered; they are executed from top to bottom. | |
2597 | # | |
2598 | # If you remove a line here THAT COMMIT WILL BE LOST. | |
2599 | # | |
2600 | # However, if you remove everything, the rebase will be aborted. | |
2601 | # | |
2602 | # Note that empty commits are commented out | |
2603 | ------------------------------------------------- | |
2604 | ||
2605 | As explained in the comments, you can reorder commits, squash them | |
2606 | together, edit commit messages, etc. by editing the list. Once you | |
2607 | are satisfied, save the list and close your editor, and the rebase | |
2608 | will begin. | |
2609 | ||
2610 | The rebase will stop where `pick` has been replaced with `edit` or | |
2611 | when a step in the list fails to mechanically resolve conflicts and | |
2612 | needs your help. When you are done editing and/or resolving conflicts | |
2613 | you can continue with `git rebase --continue`. If you decide that | |
2614 | things are getting too hairy, you can always bail out with `git rebase | |
2615 | --abort`. Even after the rebase is complete, you can still recover | |
2616 | the original branch by using the <<reflogs,reflog>>. | |
2617 | ||
2618 | For a more detailed discussion of the procedure and additional tips, | |
2619 | see the "INTERACTIVE MODE" section of linkgit:git-rebase[1]. | |
4c63ff45 | 2620 | |
e34caace | 2621 | [[patch-series-tools]] |
fd5b820d | 2622 | === Other tools |
4c63ff45 | 2623 | |
73a1d050 | 2624 | There are numerous other tools, such as StGit, which exist for the |
79c96c57 | 2625 | purpose of maintaining a patch series. These are outside of the scope of |
b181d57f | 2626 | this manual. |
4c63ff45 | 2627 | |
aa971cb9 | 2628 | [[problems-With-rewriting-history]] |
fd5b820d | 2629 | === Problems with rewriting history |
4c63ff45 | 2630 | |
b181d57f BF |
2631 | The primary problem with rewriting the history of a branch has to do |
2632 | with merging. Suppose somebody fetches your branch and merges it into | |
2633 | their branch, with a result something like this: | |
2634 | ||
1dc71a91 | 2635 | ................................................ |
b181d57f BF |
2636 | o--o--O--o--o--o <-- origin |
2637 | \ \ | |
2638 | t--t--t--m <-- their branch: | |
1dc71a91 | 2639 | ................................................ |
b181d57f BF |
2640 | |
2641 | Then suppose you modify the last three commits: | |
2642 | ||
1dc71a91 | 2643 | ................................................ |
b181d57f BF |
2644 | o--o--o <-- new head of origin |
2645 | / | |
2646 | o--o--O--o--o--o <-- old head of origin | |
1dc71a91 | 2647 | ................................................ |
b181d57f BF |
2648 | |
2649 | If we examined all this history together in one repository, it will | |
2650 | look like: | |
2651 | ||
1dc71a91 | 2652 | ................................................ |
b181d57f BF |
2653 | o--o--o <-- new head of origin |
2654 | / | |
2655 | o--o--O--o--o--o <-- old head of origin | |
2656 | \ \ | |
2657 | t--t--t--m <-- their branch: | |
1dc71a91 | 2658 | ................................................ |
b181d57f BF |
2659 | |
2660 | Git has no way of knowing that the new head is an updated version of | |
2661 | the old head; it treats this situation exactly the same as it would if | |
2662 | two developers had independently done the work on the old and new heads | |
2663 | in parallel. At this point, if someone attempts to merge the new head | |
2de9b711 | 2664 | in to their branch, Git will attempt to merge together the two (old and |
b181d57f BF |
2665 | new) lines of development, instead of trying to replace the old by the |
2666 | new. The results are likely to be unexpected. | |
2667 | ||
2668 | You may still choose to publish branches whose history is rewritten, | |
2669 | and it may be useful for others to be able to fetch those branches in | |
2670 | order to examine or test them, but they should not attempt to pull such | |
2671 | branches into their own work. | |
2672 | ||
2673 | For true distributed development that supports proper merging, | |
2674 | published branches should never be rewritten. | |
2675 | ||
3fb00282 | 2676 | [[bisect-merges]] |
fd5b820d | 2677 | === Why bisecting merge commits can be harder than bisecting linear history |
3fb00282 | 2678 | |
5162e697 | 2679 | The linkgit:git-bisect[1] command correctly handles history that |
3fb00282 SP |
2680 | includes merge commits. However, when the commit that it finds is a |
2681 | merge commit, the user may need to work harder than usual to figure out | |
2682 | why that commit introduced a problem. | |
2683 | ||
2684 | Imagine this history: | |
2685 | ||
2686 | ................................................ | |
2687 | ---Z---o---X---...---o---A---C---D | |
2688 | \ / | |
2689 | o---o---Y---...---o---B | |
2690 | ................................................ | |
2691 | ||
2692 | Suppose that on the upper line of development, the meaning of one | |
2693 | of the functions that exists at Z is changed at commit X. The | |
2694 | commits from Z leading to A change both the function's | |
2695 | implementation and all calling sites that exist at Z, as well | |
2696 | as new calling sites they add, to be consistent. There is no | |
2697 | bug at A. | |
2698 | ||
2699 | Suppose that in the meantime on the lower line of development somebody | |
2700 | adds a new calling site for that function at commit Y. The | |
2701 | commits from Z leading to B all assume the old semantics of that | |
2702 | function and the callers and the callee are consistent with each | |
2703 | other. There is no bug at B, either. | |
2704 | ||
2705 | Suppose further that the two development lines merge cleanly at C, | |
2706 | so no conflict resolution is required. | |
2707 | ||
2708 | Nevertheless, the code at C is broken, because the callers added | |
2709 | on the lower line of development have not been converted to the new | |
2710 | semantics introduced on the upper line of development. So if all | |
2711 | you know is that D is bad, that Z is good, and that | |
5162e697 | 2712 | linkgit:git-bisect[1] identifies C as the culprit, how will you |
3fb00282 SP |
2713 | figure out that the problem is due to this change in semantics? |
2714 | ||
6127c086 | 2715 | When the result of a `git bisect` is a non-merge commit, you should |
3fb00282 SP |
2716 | normally be able to discover the problem by examining just that commit. |
2717 | Developers can make this easy by breaking their changes into small | |
2718 | self-contained commits. That won't help in the case above, however, | |
2719 | because the problem isn't obvious from examination of any single | |
2720 | commit; instead, a global view of the development is required. To | |
2721 | make matters worse, the change in semantics in the problematic | |
2722 | function may be just one small part of the changes in the upper | |
2723 | line of development. | |
2724 | ||
2725 | On the other hand, if instead of merging at C you had rebased the | |
2726 | history between Z to B on top of A, you would have gotten this | |
2727 | linear history: | |
2728 | ||
2729 | ................................................................ | |
2730 | ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D* | |
2731 | ................................................................ | |
2732 | ||
2733 | Bisecting between Z and D* would hit a single culprit commit Y*, | |
2734 | and understanding why Y* was broken would probably be easier. | |
2735 | ||
2de9b711 | 2736 | Partly for this reason, many experienced Git users, even when |
3fb00282 SP |
2737 | working on an otherwise merge-heavy project, keep the history |
2738 | linear by rebasing against the latest upstream version before | |
2739 | publishing. | |
2740 | ||
e34caace | 2741 | [[advanced-branch-management]] |
fd5b820d | 2742 | == Advanced branch management |
4c63ff45 | 2743 | |
e34caace | 2744 | [[fetching-individual-branches]] |
fd5b820d | 2745 | === Fetching individual branches |
b181d57f | 2746 | |
5162e697 | 2747 | Instead of using linkgit:git-remote[1], you can also choose just |
b181d57f BF |
2748 | to update one branch at a time, and to store it locally under an |
2749 | arbitrary name: | |
2750 | ||
2751 | ------------------------------------------------- | |
2752 | $ git fetch origin todo:my-todo-work | |
2753 | ------------------------------------------------- | |
2754 | ||
1249d8ad | 2755 | The first argument, `origin`, just tells Git to fetch from the |
2de9b711 | 2756 | repository you originally cloned from. The second argument tells Git |
1249d8ad TK |
2757 | to fetch the branch named `todo` from the remote repository, and to |
2758 | store it locally under the name `refs/heads/my-todo-work`. | |
b181d57f BF |
2759 | |
2760 | You can also fetch branches from other repositories; so | |
2761 | ||
2762 | ------------------------------------------------- | |
2763 | $ git fetch git://example.com/proj.git master:example-master | |
2764 | ------------------------------------------------- | |
2765 | ||
1249d8ad TK |
2766 | will create a new branch named `example-master` and store in it the |
2767 | branch named `master` from the repository at the given URL. If you | |
b181d57f | 2768 | already have a branch named example-master, it will attempt to |
59723040 BF |
2769 | <<fast-forwards,fast-forward>> to the commit given by example.com's |
2770 | master branch. In more detail: | |
b181d57f | 2771 | |
59723040 | 2772 | [[fetch-fast-forwards]] |
fd5b820d | 2773 | === git fetch and fast-forwards |
b181d57f | 2774 | |
1249d8ad | 2775 | In the previous example, when updating an existing branch, `git fetch` |
7a7d4ef6 | 2776 | checks to make sure that the most recent commit on the remote |
b181d57f BF |
2777 | branch is a descendant of the most recent commit on your copy of the |
2778 | branch before updating your copy of the branch to point at the new | |
a75d7b54 | 2779 | commit. Git calls this process a <<fast-forwards,fast-forward>>. |
b181d57f | 2780 | |
a75d7b54 | 2781 | A fast-forward looks something like this: |
b181d57f | 2782 | |
1dc71a91 | 2783 | ................................................ |
b181d57f BF |
2784 | o--o--o--o <-- old head of the branch |
2785 | \ | |
2786 | o--o--o <-- new head of the branch | |
1dc71a91 | 2787 | ................................................ |
b181d57f BF |
2788 | |
2789 | ||
2790 | In some cases it is possible that the new head will *not* actually be | |
2791 | a descendant of the old head. For example, the developer may have | |
2792 | realized she made a serious mistake, and decided to backtrack, | |
2793 | resulting in a situation like: | |
2794 | ||
1dc71a91 | 2795 | ................................................ |
b181d57f BF |
2796 | o--o--o--o--a--b <-- old head of the branch |
2797 | \ | |
2798 | o--o--o <-- new head of the branch | |
1dc71a91 | 2799 | ................................................ |
b181d57f | 2800 | |
1249d8ad | 2801 | In this case, `git fetch` will fail, and print out a warning. |
b181d57f | 2802 | |
2de9b711 | 2803 | In that case, you can still force Git to update to the new head, as |
b181d57f | 2804 | described in the following section. However, note that in the |
1249d8ad | 2805 | situation above this may mean losing the commits labeled `a` and `b`, |
b181d57f BF |
2806 | unless you've already created a reference of your own pointing to |
2807 | them. | |
2808 | ||
e34caace | 2809 | [[forcing-fetch]] |
fd5b820d | 2810 | === Forcing git fetch to do non-fast-forward updates |
b181d57f BF |
2811 | |
2812 | If git fetch fails because the new head of a branch is not a | |
2813 | descendant of the old head, you may force the update with: | |
2814 | ||
2815 | ------------------------------------------------- | |
2816 | $ git fetch git://example.com/proj.git +master:refs/remotes/example/master | |
2817 | ------------------------------------------------- | |
2818 | ||
1249d8ad | 2819 | Note the addition of the `+` sign. Alternatively, you can use the `-f` |
c64415e2 BF |
2820 | flag to force updates of all the fetched branches, as in: |
2821 | ||
2822 | ------------------------------------------------- | |
2823 | $ git fetch -f origin | |
2824 | ------------------------------------------------- | |
2825 | ||
2826 | Be aware that commits that the old version of example/master pointed at | |
2827 | may be lost, as we saw in the previous section. | |
b181d57f | 2828 | |
e34caace | 2829 | [[remote-branch-configuration]] |
fd5b820d | 2830 | === Configuring remote-tracking branches |
b181d57f | 2831 | |
1249d8ad | 2832 | We saw above that `origin` is just a shortcut to refer to the |
79c96c57 | 2833 | repository that you originally cloned from. This information is |
2de9b711 | 2834 | stored in Git configuration variables, which you can see using |
5162e697 | 2835 | linkgit:git-config[1]: |
b181d57f BF |
2836 | |
2837 | ------------------------------------------------- | |
9d13bda3 | 2838 | $ git config -l |
b181d57f BF |
2839 | core.repositoryformatversion=0 |
2840 | core.filemode=true | |
2841 | core.logallrefupdates=true | |
2842 | remote.origin.url=git://git.kernel.org/pub/scm/git/git.git | |
2843 | remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* | |
2844 | branch.master.remote=origin | |
2845 | branch.master.merge=refs/heads/master | |
2846 | ------------------------------------------------- | |
2847 | ||
2848 | If there are other repositories that you also use frequently, you can | |
2849 | create similar configuration options to save typing; for example, | |
b181d57f BF |
2850 | |
2851 | ------------------------------------------------- | |
47adb8ac | 2852 | $ git remote add example git://example.com/proj.git |
b181d57f BF |
2853 | ------------------------------------------------- |
2854 | ||
47adb8ac | 2855 | adds the following to `.git/config`: |
b181d57f BF |
2856 | |
2857 | ------------------------------------------------- | |
47adb8ac TK |
2858 | [remote "example"] |
2859 | url = git://example.com/proj.git | |
2860 | fetch = +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2861 | ------------------------------------------------- |
2862 | ||
47adb8ac TK |
2863 | Also note that the above configuration can be performed by directly |
2864 | editing the file `.git/config` instead of using linkgit:git-remote[1]. | |
b181d57f | 2865 | |
47adb8ac TK |
2866 | After configuring the remote, the following three commands will do the |
2867 | same thing: | |
b181d57f BF |
2868 | |
2869 | ------------------------------------------------- | |
47adb8ac TK |
2870 | $ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/* |
2871 | $ git fetch example +refs/heads/*:refs/remotes/example/* | |
b181d57f BF |
2872 | $ git fetch example |
2873 | ------------------------------------------------- | |
2874 | ||
5162e697 | 2875 | See linkgit:git-config[1] for more details on the configuration |
47adb8ac TK |
2876 | options mentioned above and linkgit:git-fetch[1] for more details on |
2877 | the refspec syntax. | |
d19fbc3c | 2878 | |
d19fbc3c | 2879 | |
036f8199 | 2880 | [[git-concepts]] |
fd5b820d | 2881 | == Git concepts |
d19fbc3c | 2882 | |
036f8199 BF |
2883 | Git is built on a small number of simple but powerful ideas. While it |
2884 | is possible to get things done without understanding them, you will find | |
2de9b711 | 2885 | Git much more intuitive if you do. |
036f8199 BF |
2886 | |
2887 | We start with the most important, the <<def_object_database,object | |
2888 | database>> and the <<def_index,index>>. | |
b181d57f | 2889 | |
e34caace | 2890 | [[the-object-database]] |
fd5b820d | 2891 | === The Object Database |
b181d57f | 2892 | |
1bbf1c79 BF |
2893 | |
2894 | We already saw in <<understanding-commits>> that all commits are stored | |
2895 | under a 40-digit "object name". In fact, all the information needed to | |
2896 | represent the history of a project is stored in objects with such names. | |
a6e5ef7d FC |
2897 | In each case the name is calculated by taking the SHA-1 hash of the |
2898 | contents of the object. The SHA-1 hash is a cryptographic hash function. | |
1bbf1c79 BF |
2899 | What that means to us is that it is impossible to find two different |
2900 | objects with the same name. This has a number of advantages; among | |
2901 | others: | |
2902 | ||
2903 | - Git can quickly determine whether two objects are identical or not, | |
2904 | just by comparing names. | |
06ada152 | 2905 | - Since object names are computed the same way in every repository, the |
1bbf1c79 BF |
2906 | same content stored in two repositories will always be stored under |
2907 | the same name. | |
2908 | - Git can detect errors when it reads an object, by checking that the | |
a6e5ef7d | 2909 | object's name is still the SHA-1 hash of its contents. |
1bbf1c79 BF |
2910 | |
2911 | (See <<object-details>> for the details of the object formatting and | |
a6e5ef7d | 2912 | SHA-1 calculation.) |
1bbf1c79 BF |
2913 | |
2914 | There are four different types of objects: "blob", "tree", "commit", and | |
2915 | "tag". | |
2916 | ||
2917 | - A <<def_blob_object,"blob" object>> is used to store file data. | |
843c81dc | 2918 | - A <<def_tree_object,"tree" object>> ties one or more |
1bbf1c79 BF |
2919 | "blob" objects into a directory structure. In addition, a tree object |
2920 | can refer to other tree objects, thus creating a directory hierarchy. | |
2921 | - A <<def_commit_object,"commit" object>> ties such directory hierarchies | |
2ef8ac1b | 2922 | together into a <<def_DAG,directed acyclic graph>> of revisions--each |
1bbf1c79 BF |
2923 | commit contains the object name of exactly one tree designating the |
2924 | directory hierarchy at the time of the commit. In addition, a commit | |
2925 | refers to "parent" commit objects that describe the history of how we | |
2926 | arrived at that directory hierarchy. | |
2927 | - A <<def_tag_object,"tag" object>> symbolically identifies and can be | |
2928 | used to sign other objects. It contains the object name and type of | |
2929 | another object, a symbolic name (of course!) and, optionally, a | |
2930 | signature. | |
b181d57f | 2931 | |
b181d57f BF |
2932 | The object types in some more detail: |
2933 | ||
513d419c | 2934 | [[commit-object]] |
fd5b820d | 2935 | ==== Commit Object |
b181d57f | 2936 | |
1bbf1c79 | 2937 | The "commit" object links a physical state of a tree with a description |
1249d8ad | 2938 | of how we got there and why. Use the `--pretty=raw` option to |
5162e697 | 2939 | linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite |
1bbf1c79 BF |
2940 | commit: |
2941 | ||
2942 | ------------------------------------------------ | |
2943 | $ git show -s --pretty=raw 2be7fcb476 | |
2944 | commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4 | |
2945 | tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf | |
2946 | parent 257a84d9d02e90447b149af58b271c19405edb6a | |
2947 | author Dave Watson <dwatson@mimvista.com> 1187576872 -0400 | |
2948 | committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700 | |
2949 | ||
2950 | Fix misspelling of 'suppress' in docs | |
2951 | ||
2952 | Signed-off-by: Junio C Hamano <gitster@pobox.com> | |
2953 | ------------------------------------------------ | |
2954 | ||
2955 | As you can see, a commit is defined by: | |
2956 | ||
a6e5ef7d | 2957 | - a tree: The SHA-1 name of a tree object (as defined below), representing |
1bbf1c79 | 2958 | the contents of a directory at a certain point in time. |
edfbbf7e | 2959 | - parent(s): The SHA-1 name(s) of some number of commits which represent the |
9e5d87d4 | 2960 | immediately previous step(s) in the history of the project. The |
1bbf1c79 BF |
2961 | example above has one parent; merge commits may have more than |
2962 | one. A commit with no parents is called a "root" commit, and | |
2963 | represents the initial revision of a project. Each project must have | |
2964 | at least one root. A project can also have multiple roots, though | |
2965 | that isn't common (or necessarily a good idea). | |
2966 | - an author: The name of the person responsible for this change, together | |
2967 | with its date. | |
2968 | - a committer: The name of the person who actually created the commit, | |
2969 | with the date it was done. This may be different from the author, for | |
2970 | example, if the author was someone who wrote a patch and emailed it | |
2971 | to the person who used it to create the commit. | |
2972 | - a comment describing this commit. | |
2973 | ||
2974 | Note that a commit does not itself contain any information about what | |
2975 | actually changed; all changes are calculated by comparing the contents | |
2976 | of the tree referred to by this commit with the trees associated with | |
2de9b711 | 2977 | its parents. In particular, Git does not attempt to record file renames |
1bbf1c79 BF |
2978 | explicitly, though it can identify cases where the existence of the same |
2979 | file data at changing paths suggests a rename. (See, for example, the | |
1249d8ad | 2980 | `-M` option to linkgit:git-diff[1]). |
1bbf1c79 | 2981 | |
5162e697 | 2982 | A commit is usually created by linkgit:git-commit[1], which creates a |
1bbf1c79 BF |
2983 | commit whose parent is normally the current HEAD, and whose tree is |
2984 | taken from the content currently stored in the index. | |
b181d57f | 2985 | |
e34caace | 2986 | [[tree-object]] |
fd5b820d | 2987 | ==== Tree Object |
b181d57f | 2988 | |
5162e697 DM |
2989 | The ever-versatile linkgit:git-show[1] command can also be used to |
2990 | examine tree objects, but linkgit:git-ls-tree[1] will give you more | |
1bbf1c79 BF |
2991 | details: |
2992 | ||
2993 | ------------------------------------------------ | |
2994 | $ git ls-tree fb3a8bdd0ce | |
2995 | 100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore | |
2996 | 100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap | |
2997 | 100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING | |
2998 | 040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation | |
2999 | 100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN | |
3000 | 100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL | |
3001 | 100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile | |
3002 | 100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README | |
3003 | ... | |
3004 | ------------------------------------------------ | |
3005 | ||
3006 | As you can see, a tree object contains a list of entries, each with a | |
a6e5ef7d | 3007 | mode, object type, SHA-1 name, and name, sorted by name. It represents |
1bbf1c79 BF |
3008 | the contents of a single directory tree. |
3009 | ||
3010 | The object type may be a blob, representing the contents of a file, or | |
3011 | another tree, representing the contents of a subdirectory. Since trees | |
a6e5ef7d FC |
3012 | and blobs, like all other objects, are named by the SHA-1 hash of their |
3013 | contents, two trees have the same SHA-1 name if and only if their | |
1bbf1c79 | 3014 | contents (including, recursively, the contents of all subdirectories) |
2de9b711 | 3015 | are identical. This allows Git to quickly determine the differences |
1bbf1c79 BF |
3016 | between two related tree objects, since it can ignore any entries with |
3017 | identical object names. | |
3018 | ||
3019 | (Note: in the presence of submodules, trees may also have commits as | |
6dd14366 | 3020 | entries. See <<submodules>> for documentation.) |
1bbf1c79 | 3021 | |
2de9b711 | 3022 | Note that the files all have mode 644 or 755: Git actually only pays |
1bbf1c79 | 3023 | attention to the executable bit. |
b181d57f | 3024 | |
513d419c | 3025 | [[blob-object]] |
fd5b820d | 3026 | ==== Blob Object |
b181d57f | 3027 | |
5162e697 | 3028 | You can use linkgit:git-show[1] to examine the contents of a blob; take, |
1249d8ad | 3029 | for example, the blob in the entry for `COPYING` from the tree above: |
b181d57f | 3030 | |
1bbf1c79 BF |
3031 | ------------------------------------------------ |
3032 | $ git show 6ff87c4664 | |
3033 | ||
3034 | Note that the only valid version of the GPL as far as this project | |
3035 | is concerned is _this_ particular version of the license (ie v2, not | |
3036 | v2.2 or v3.x or whatever), unless explicitly otherwise stated. | |
3037 | ... | |
3038 | ------------------------------------------------ | |
b181d57f | 3039 | |
1bbf1c79 BF |
3040 | A "blob" object is nothing but a binary blob of data. It doesn't refer |
3041 | to anything else or have attributes of any kind. | |
3042 | ||
3043 | Since the blob is entirely defined by its data, if two files in a | |
3044 | directory tree (or in multiple different versions of the repository) | |
3045 | have the same contents, they will share the same blob object. The object | |
3046 | is totally independent of its location in the directory tree, and | |
3047 | renaming a file does not change the object that file is associated with. | |
3048 | ||
3049 | Note that any tree or blob object can be examined using | |
5162e697 | 3050 | linkgit:git-show[1] with the <revision>:<path> syntax. This can |
1bbf1c79 BF |
3051 | sometimes be useful for browsing the contents of a tree that is not |
3052 | currently checked out. | |
b181d57f | 3053 | |
e34caace | 3054 | [[trust]] |
fd5b820d | 3055 | ==== Trust |
b181d57f | 3056 | |
a6e5ef7d | 3057 | If you receive the SHA-1 name of a blob from one source, and its contents |
1bbf1c79 | 3058 | from another (possibly untrusted) source, you can still trust that those |
a6e5ef7d FC |
3059 | contents are correct as long as the SHA-1 name agrees. This is because |
3060 | the SHA-1 is designed so that it is infeasible to find different contents | |
1bbf1c79 | 3061 | that produce the same hash. |
b181d57f | 3062 | |
a6e5ef7d | 3063 | Similarly, you need only trust the SHA-1 name of a top-level tree object |
1bbf1c79 | 3064 | to trust the contents of the entire directory that it refers to, and if |
a6e5ef7d | 3065 | you receive the SHA-1 name of a commit from a trusted source, then you |
1bbf1c79 BF |
3066 | can easily verify the entire history of commits reachable through |
3067 | parents of that commit, and all of those contents of the trees referred | |
3068 | to by those commits. | |
b181d57f BF |
3069 | |
3070 | So to introduce some real trust in the system, the only thing you need | |
3071 | to do is to digitally sign just 'one' special note, which includes the | |
3072 | name of a top-level commit. Your digital signature shows others | |
3073 | that you trust that commit, and the immutability of the history of | |
3074 | commits tells others that they can trust the whole history. | |
3075 | ||
3076 | In other words, you can easily validate a whole archive by just | |
a6e5ef7d | 3077 | sending out a single email that tells the people the name (SHA-1 hash) |
b181d57f BF |
3078 | of the top commit, and digitally sign that email using something |
3079 | like GPG/PGP. | |
3080 | ||
2de9b711 | 3081 | To assist in this, Git also provides the tag object... |
b181d57f | 3082 | |
e34caace | 3083 | [[tag-object]] |
fd5b820d | 3084 | ==== Tag Object |
b181d57f | 3085 | |
1bbf1c79 BF |
3086 | A tag object contains an object, object type, tag name, the name of the |
3087 | person ("tagger") who created the tag, and a message, which may contain | |
843c81dc | 3088 | a signature, as can be seen using linkgit:git-cat-file[1]: |
b181d57f | 3089 | |
1bbf1c79 BF |
3090 | ------------------------------------------------ |
3091 | $ git cat-file tag v1.5.0 | |
3092 | object 437b1b20df4b356c9342dac8d38849f24ef44f27 | |
3093 | type commit | |
3094 | tag v1.5.0 | |
3095 | tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000 | |
3096 | ||
3097 | GIT 1.5.0 | |
3098 | -----BEGIN PGP SIGNATURE----- | |
3099 | Version: GnuPG v1.4.6 (GNU/Linux) | |
3100 | ||
3101 | iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui | |
3102 | nLE/L9aUXdWeTFPron96DLA= | |
3103 | =2E+0 | |
3104 | -----END PGP SIGNATURE----- | |
3105 | ------------------------------------------------ | |
b181d57f | 3106 | |
5162e697 DM |
3107 | See the linkgit:git-tag[1] command to learn how to create and verify tag |
3108 | objects. (Note that linkgit:git-tag[1] can also be used to create | |
1bbf1c79 | 3109 | "lightweight tags", which are not tag objects at all, but just simple |
1249d8ad | 3110 | references whose names begin with `refs/tags/`). |
b181d57f | 3111 | |
09eff7b0 | 3112 | [[pack-files]] |
fd5b820d | 3113 | ==== How Git stores objects efficiently: pack files |
09eff7b0 | 3114 | |
9644ffdd | 3115 | Newly created objects are initially created in a file named after the |
1249d8ad | 3116 | object's SHA-1 hash (stored in `.git/objects`). |
09eff7b0 BF |
3117 | |
3118 | Unfortunately this system becomes inefficient once a project has a | |
3119 | lot of objects. Try this on an old project: | |
3120 | ||
3121 | ------------------------------------------------ | |
3122 | $ git count-objects | |
3123 | 6930 objects, 47620 kilobytes | |
3124 | ------------------------------------------------ | |
3125 | ||
3126 | The first number is the number of objects which are kept in | |
3127 | individual files. The second is the amount of space taken up by | |
3128 | those "loose" objects. | |
3129 | ||
2de9b711 | 3130 | You can save space and make Git faster by moving these loose objects in |
09eff7b0 BF |
3131 | to a "pack file", which stores a group of objects in an efficient |
3132 | compressed format; the details of how pack files are formatted can be | |
d5ff3b4b | 3133 | found in link:technical/pack-format.html[pack format]. |
09eff7b0 BF |
3134 | |
3135 | To put the loose objects into a pack, just run git repack: | |
3136 | ||
3137 | ------------------------------------------------ | |
3138 | $ git repack | |
3e65ac49 TA |
3139 | Counting objects: 6020, done. |
3140 | Delta compression using up to 4 threads. | |
3141 | Compressing objects: 100% (6020/6020), done. | |
3142 | Writing objects: 100% (6020/6020), done. | |
3143 | Total 6020 (delta 4070), reused 0 (delta 0) | |
09eff7b0 BF |
3144 | ------------------------------------------------ |
3145 | ||
3e65ac49 TA |
3146 | This creates a single "pack file" in .git/objects/pack/ |
3147 | containing all currently unpacked objects. You can then run | |
09eff7b0 BF |
3148 | |
3149 | ------------------------------------------------ | |
3150 | $ git prune | |
3151 | ------------------------------------------------ | |
3152 | ||
3153 | to remove any of the "loose" objects that are now contained in the | |
3154 | pack. This will also remove any unreferenced objects (which may be | |
1249d8ad | 3155 | created when, for example, you use `git reset` to remove a commit). |
09eff7b0 | 3156 | You can verify that the loose objects are gone by looking at the |
1249d8ad | 3157 | `.git/objects` directory or by running |
09eff7b0 BF |
3158 | |
3159 | ------------------------------------------------ | |
3160 | $ git count-objects | |
3161 | 0 objects, 0 kilobytes | |
3162 | ------------------------------------------------ | |
3163 | ||
3164 | Although the object files are gone, any commands that refer to those | |
3165 | objects will work exactly as they did before. | |
3166 | ||
5162e697 | 3167 | The linkgit:git-gc[1] command performs packing, pruning, and more for |
09eff7b0 BF |
3168 | you, so is normally the only high-level command you need. |
3169 | ||
3170 | [[dangling-objects]] | |
fd5b820d | 3171 | ==== Dangling objects |
09eff7b0 | 3172 | |
5162e697 | 3173 | The linkgit:git-fsck[1] command will sometimes complain about dangling |
09eff7b0 BF |
3174 | objects. They are not a problem. |
3175 | ||
3176 | The most common cause of dangling objects is that you've rebased a | |
3177 | branch, or you have pulled from somebody else who rebased a branch--see | |
3178 | <<cleaning-up-history>>. In that case, the old head of the original | |
3179 | branch still exists, as does everything it pointed to. The branch | |
3180 | pointer itself just doesn't, since you replaced it with another one. | |
3181 | ||
3182 | There are also other situations that cause dangling objects. For | |
1249d8ad | 3183 | example, a "dangling blob" may arise because you did a `git add` of a |
09eff7b0 BF |
3184 | file, but then, before you actually committed it and made it part of the |
3185 | bigger picture, you changed something else in that file and committed | |
2ef8ac1b | 3186 | that *updated* thing--the old state that you added originally ends up |
09eff7b0 BF |
3187 | not being pointed to by any commit or tree, so it's now a dangling blob |
3188 | object. | |
3189 | ||
3190 | Similarly, when the "recursive" merge strategy runs, and finds that | |
3191 | there are criss-cross merges and thus more than one merge base (which is | |
3192 | fairly unusual, but it does happen), it will generate one temporary | |
3193 | midway tree (or possibly even more, if you had lots of criss-crossing | |
3194 | merges and more than two merge bases) as a temporary internal merge | |
3195 | base, and again, those are real objects, but the end result will not end | |
3196 | up pointing to them, so they end up "dangling" in your repository. | |
3197 | ||
3198 | Generally, dangling objects aren't anything to worry about. They can | |
3199 | even be very useful: if you screw something up, the dangling objects can | |
3200 | be how you recover your old tree (say, you did a rebase, and realized | |
2ef8ac1b | 3201 | that you really didn't want to--you can look at what dangling objects |
09eff7b0 BF |
3202 | you have, and decide to reset your head to some old dangling state). |
3203 | ||
3204 | For commits, you can just use: | |
3205 | ||
3206 | ------------------------------------------------ | |
3207 | $ gitk <dangling-commit-sha-goes-here> --not --all | |
3208 | ------------------------------------------------ | |
3209 | ||
3210 | This asks for all the history reachable from the given commit but not | |
3211 | from any branch, tag, or other reference. If you decide it's something | |
3212 | you want, you can always create a new reference to it, e.g., | |
3213 | ||
3214 | ------------------------------------------------ | |
3215 | $ git branch recovered-branch <dangling-commit-sha-goes-here> | |
3216 | ------------------------------------------------ | |
3217 | ||
3218 | For blobs and trees, you can't do the same, but you can still examine | |
3219 | them. You can just do | |
3220 | ||
3221 | ------------------------------------------------ | |
3222 | $ git show <dangling-blob/tree-sha-goes-here> | |
3223 | ------------------------------------------------ | |
3224 | ||
3225 | to show what the contents of the blob were (or, for a tree, basically | |
1249d8ad | 3226 | what the `ls` for that directory was), and that may give you some idea |
09eff7b0 BF |
3227 | of what the operation was that left that dangling object. |
3228 | ||
3229 | Usually, dangling blobs and trees aren't very interesting. They're | |
3230 | almost always the result of either being a half-way mergebase (the blob | |
3231 | will often even have the conflict markers from a merge in it, if you | |
3232 | have had conflicting merges that you fixed up by hand), or simply | |
1249d8ad | 3233 | because you interrupted a `git fetch` with ^C or something like that, |
09eff7b0 BF |
3234 | leaving _some_ of the new objects in the object database, but just |
3235 | dangling and useless. | |
3236 | ||
3237 | Anyway, once you are sure that you're not interested in any dangling | |
3238 | state, you can just prune all unreachable objects: | |
3239 | ||
3240 | ------------------------------------------------ | |
3241 | $ git prune | |
3242 | ------------------------------------------------ | |
3243 | ||
ddeb817f | 3244 | and they'll be gone. (You should only run `git prune` on a quiescent |
2ef8ac1b | 3245 | repository--it's kind of like doing a filesystem fsck recovery: you |
09eff7b0 | 3246 | don't want to do that while the filesystem is mounted. |
ddeb817f TA |
3247 | `git prune` is designed not to cause any harm in such cases of concurrent |
3248 | accesses to a repository but you might receive confusing or scary messages.) | |
b181d57f | 3249 | |
1cdade2c | 3250 | [[recovering-from-repository-corruption]] |
fd5b820d | 3251 | ==== Recovering from repository corruption |
1cdade2c | 3252 | |
2de9b711 TA |
3253 | By design, Git treats data trusted to it with caution. However, even in |
3254 | the absence of bugs in Git itself, it is still possible that hardware or | |
1cdade2c BF |
3255 | operating system errors could corrupt data. |
3256 | ||
3257 | The first defense against such problems is backups. You can back up a | |
2de9b711 | 3258 | Git directory using clone, or just using cp, tar, or any other backup |
1cdade2c BF |
3259 | mechanism. |
3260 | ||
3261 | As a last resort, you can search for the corrupted objects and attempt | |
3262 | to replace them by hand. Back up your repository before attempting this | |
3263 | in case you corrupt things even more in the process. | |
3264 | ||
3265 | We'll assume that the problem is a single missing or corrupted blob, | |
9e5d87d4 | 3266 | which is sometimes a solvable problem. (Recovering missing trees and |
1cdade2c BF |
3267 | especially commits is *much* harder). |
3268 | ||
3269 | Before starting, verify that there is corruption, and figure out where | |
5162e697 | 3270 | it is with linkgit:git-fsck[1]; this may be time-consuming. |
1cdade2c BF |
3271 | |
3272 | Assume the output looks like this: | |
3273 | ||
3274 | ------------------------------------------------ | |
c6a13b2c | 3275 | $ git fsck --full --no-dangling |
1cdade2c BF |
3276 | broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 |
3277 | to blob 4b9458b3786228369c63936db65827de3cc06200 | |
3278 | missing blob 4b9458b3786228369c63936db65827de3cc06200 | |
3279 | ------------------------------------------------ | |
3280 | ||
1cdade2c BF |
3281 | Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6 |
3282 | points to it. If you could find just one copy of that missing blob | |
3283 | object, possibly in some other repository, you could move it into | |
1249d8ad | 3284 | `.git/objects/4b/9458b3...` and be done. Suppose you can't. You can |
5162e697 | 3285 | still examine the tree that pointed to it with linkgit:git-ls-tree[1], |
1cdade2c BF |
3286 | which might output something like: |
3287 | ||
3288 | ------------------------------------------------ | |
3289 | $ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 | |
3290 | 100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore | |
3291 | 100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap | |
3292 | 100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING | |
3293 | ... | |
3294 | 100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile | |
3295 | ... | |
3296 | ------------------------------------------------ | |
3297 | ||
3298 | So now you know that the missing blob was the data for a file named | |
1249d8ad TK |
3299 | `myfile`. And chances are you can also identify the directory--let's |
3300 | say it's in `somedirectory`. If you're lucky the missing copy might be | |
1cdade2c | 3301 | the same as the copy you have checked out in your working tree at |
1249d8ad | 3302 | `somedirectory/myfile`; you can test whether that's right with |
5162e697 | 3303 | linkgit:git-hash-object[1]: |
1cdade2c BF |
3304 | |
3305 | ------------------------------------------------ | |
3306 | $ git hash-object -w somedirectory/myfile | |
3307 | ------------------------------------------------ | |
3308 | ||
3309 | which will create and store a blob object with the contents of | |
a6e5ef7d | 3310 | somedirectory/myfile, and output the SHA-1 of that object. if you're |
1cdade2c BF |
3311 | extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in |
3312 | which case you've guessed right, and the corruption is fixed! | |
3313 | ||
3314 | Otherwise, you need more information. How do you tell which version of | |
3315 | the file has been lost? | |
3316 | ||
3317 | The easiest way to do this is with: | |
3318 | ||
3319 | ------------------------------------------------ | |
3320 | $ git log --raw --all --full-history -- somedirectory/myfile | |
3321 | ------------------------------------------------ | |
3322 | ||
3323 | Because you're asking for raw output, you'll now get something like | |
3324 | ||
3325 | ------------------------------------------------ | |
3326 | commit abc | |
3327 | Author: | |
3328 | Date: | |
3329 | ... | |
f61d89e1 | 3330 | :100644 100644 4b9458b newsha M somedirectory/myfile |
1cdade2c BF |
3331 | |
3332 | ||
3333 | commit xyz | |
3334 | Author: | |
3335 | Date: | |
3336 | ||
3337 | ... | |
f61d89e1 | 3338 | :100644 100644 oldsha 4b9458b M somedirectory/myfile |
1cdade2c BF |
3339 | ------------------------------------------------ |
3340 | ||
edfbbf7e ŠN |
3341 | This tells you that the immediately following version of the file was |
3342 | "newsha", and that the immediately preceding version was "oldsha". | |
1cdade2c BF |
3343 | You also know the commit messages that went with the change from oldsha |
3344 | to 4b9458b and with the change from 4b9458b to newsha. | |
3345 | ||
3346 | If you've been committing small enough changes, you may now have a good | |
3347 | shot at reconstructing the contents of the in-between state 4b9458b. | |
3348 | ||
3349 | If you can do that, you can now recreate the missing object with | |
3350 | ||
3351 | ------------------------------------------------ | |
3352 | $ git hash-object -w <recreated-file> | |
3353 | ------------------------------------------------ | |
3354 | ||
3355 | and your repository is good again! | |
3356 | ||
1249d8ad | 3357 | (Btw, you could have ignored the `fsck`, and started with doing a |
1cdade2c BF |
3358 | |
3359 | ------------------------------------------------ | |
3360 | $ git log --raw --all | |
3361 | ------------------------------------------------ | |
3362 | ||
f61d89e1 | 3363 | and just looked for the sha of the missing object (4b9458b) in that |
da2c7b3d | 3364 | whole thing. It's up to you--Git does *have* a lot of information, it is |
1cdade2c BF |
3365 | just missing one particular blob version. |
3366 | ||
e34caace | 3367 | [[the-index]] |
fd5b820d | 3368 | === The index |
1c097891 | 3369 | |
1249d8ad | 3370 | The index is a binary file (generally kept in `.git/index`) containing a |
a6e5ef7d | 3371 | sorted list of path names, each with permissions and the SHA-1 of a blob |
5162e697 | 3372 | object; linkgit:git-ls-files[1] can show you the contents of the index: |
b181d57f | 3373 | |
1c097891 BF |
3374 | ------------------------------------------------- |
3375 | $ git ls-files --stage | |
3376 | 100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore | |
3377 | 100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap | |
3378 | 100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING | |
3379 | 100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore | |
3380 | 100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile | |
3381 | ... | |
3382 | 100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h | |
3383 | 100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c | |
3384 | 100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h | |
3385 | ------------------------------------------------- | |
3386 | ||
3387 | Note that in older documentation you may see the index called the | |
3388 | "current directory cache" or just the "cache". It has three important | |
3389 | properties: | |
3390 | ||
3391 | 1. The index contains all the information necessary to generate a single | |
3392 | (uniquely determined) tree object. | |
3393 | + | |
5162e697 | 3394 | For example, running linkgit:git-commit[1] generates this tree object |
1c097891 BF |
3395 | from the index, stores it in the object database, and uses it as the |
3396 | tree object associated with the new commit. | |
3397 | ||
3398 | 2. The index enables fast comparisons between the tree object it defines | |
3399 | and the working tree. | |
3400 | + | |
3401 | It does this by storing some additional data for each entry (such as | |
3402 | the last modified time). This data is not displayed above, and is not | |
3403 | stored in the created tree object, but it can be used to determine | |
3404 | quickly which files in the working directory differ from what was | |
2de9b711 | 3405 | stored in the index, and thus save Git from having to read all of the |
1c097891 BF |
3406 | data from such files to look for changes. |
3407 | ||
3408 | 3. It can efficiently represent information about merge conflicts | |
3409 | between different tree objects, allowing each pathname to be | |
b181d57f | 3410 | associated with sufficient information about the trees involved that |
1c097891 BF |
3411 | you can create a three-way merge between them. |
3412 | + | |
3413 | We saw in <<conflict-resolution>> that during a merge the index can | |
3414 | store multiple versions of a single file (called "stages"). The third | |
5162e697 | 3415 | column in the linkgit:git-ls-files[1] output above is the stage |
1c097891 BF |
3416 | number, and will take on values other than 0 for files with merge |
3417 | conflicts. | |
3418 | ||
3419 | The index is thus a sort of temporary staging area, which is filled with | |
3420 | a tree which you are in the process of working on. | |
3421 | ||
3422 | If you blow the index away entirely, you generally haven't lost any | |
3423 | information as long as you have the name of the tree that it described. | |
b181d57f | 3424 | |
38a457ba | 3425 | [[submodules]] |
fd5b820d | 3426 | == Submodules |
38a457ba | 3427 | |
6dd14366 MS |
3428 | Large projects are often composed of smaller, self-contained modules. For |
3429 | example, an embedded Linux distribution's source tree would include every | |
3430 | piece of software in the distribution with some local modifications; a movie | |
3431 | player might need to build against a specific, known-working version of a | |
3432 | decompression library; several independent programs might all share the same | |
3433 | build scripts. | |
3434 | ||
3435 | With centralized revision control systems this is often accomplished by | |
3436 | including every module in one single repository. Developers can check out | |
3437 | all modules or only the modules they need to work with. They can even modify | |
3438 | files across several modules in a single commit while moving things around | |
3439 | or updating APIs and translations. | |
3440 | ||
3441 | Git does not allow partial checkouts, so duplicating this approach in Git | |
3442 | would force developers to keep a local copy of modules they are not | |
3443 | interested in touching. Commits in an enormous checkout would be slower | |
3444 | than you'd expect as Git would have to scan every directory for changes. | |
3445 | If modules have a lot of local history, clones would take forever. | |
3446 | ||
3447 | On the plus side, distributed revision control systems can much better | |
3448 | integrate with external sources. In a centralized model, a single arbitrary | |
3449 | snapshot of the external project is exported from its own revision control | |
3450 | and then imported into the local revision control on a vendor branch. All | |
3451 | the history is hidden. With distributed revision control you can clone the | |
3452 | entire external history and much more easily follow development and re-merge | |
3453 | local changes. | |
3454 | ||
3455 | Git's submodule support allows a repository to contain, as a subdirectory, a | |
3456 | checkout of an external project. Submodules maintain their own identity; | |
3457 | the submodule support just stores the submodule repository location and | |
3458 | commit ID, so other developers who clone the containing project | |
3459 | ("superproject") can easily clone all the submodules at the same revision. | |
3460 | Partial checkouts of the superproject are possible: you can tell Git to | |
3461 | clone none, some or all of the submodules. | |
3462 | ||
5162e697 | 3463 | The linkgit:git-submodule[1] command is available since Git 1.5.3. Users |
6dd14366 MS |
3464 | with Git 1.5.2 can look up the submodule commits in the repository and |
3465 | manually check them out; earlier versions won't recognize the submodules at | |
3466 | all. | |
38a457ba | 3467 | |
ddd4ddef | 3468 | To see how submodule support works, create four example |
38a457ba MV |
3469 | repositories that can be used later as a submodule: |
3470 | ||
3471 | ------------------------------------------------- | |
3472 | $ mkdir ~/git | |
3473 | $ cd ~/git | |
3474 | $ for i in a b c d | |
3475 | do | |
3476 | mkdir $i | |
3477 | cd $i | |
3478 | git init | |
3479 | echo "module $i" > $i.txt | |
3480 | git add $i.txt | |
3481 | git commit -m "Initial commit, submodule $i" | |
3482 | cd .. | |
3483 | done | |
3484 | ------------------------------------------------- | |
3485 | ||
3486 | Now create the superproject and add all the submodules: | |
3487 | ||
3488 | ------------------------------------------------- | |
3489 | $ mkdir super | |
3490 | $ cd super | |
3491 | $ git init | |
3492 | $ for i in a b c d | |
3493 | do | |
a56bf585 | 3494 | git submodule add ~/git/$i $i |
38a457ba MV |
3495 | done |
3496 | ------------------------------------------------- | |
3497 | ||
3498 | NOTE: Do not use local URLs here if you plan to publish your superproject! | |
3499 | ||
6127c086 | 3500 | See what files `git submodule` created: |
38a457ba MV |
3501 | |
3502 | ------------------------------------------------- | |
3503 | $ ls -a | |
3504 | . .. .git .gitmodules a b c d | |
3505 | ------------------------------------------------- | |
3506 | ||
6127c086 | 3507 | The `git submodule add <repo> <path>` command does a couple of things: |
38a457ba | 3508 | |
1249d8ad | 3509 | - It clones the submodule from `<repo>` to the given `<path>` under the |
a56bf585 | 3510 | current directory and by default checks out the master branch. |
5162e697 | 3511 | - It adds the submodule's clone path to the linkgit:gitmodules[5] file and |
6dd14366 | 3512 | adds this file to the index, ready to be committed. |
38a457ba MV |
3513 | - It adds the submodule's current commit ID to the index, ready to be |
3514 | committed. | |
3515 | ||
3516 | Commit the superproject: | |
3517 | ||
3518 | ------------------------------------------------- | |
3519 | $ git commit -m "Add submodules a, b, c and d." | |
3520 | ------------------------------------------------- | |
3521 | ||
3522 | Now clone the superproject: | |
3523 | ||
3524 | ------------------------------------------------- | |
3525 | $ cd .. | |
3526 | $ git clone super cloned | |
3527 | $ cd cloned | |
3528 | ------------------------------------------------- | |
3529 | ||
3530 | The submodule directories are there, but they're empty: | |
3531 | ||
3532 | ------------------------------------------------- | |
3533 | $ ls -a a | |
3534 | . .. | |
3535 | $ git submodule status | |
3536 | -d266b9873ad50488163457f025db7cdd9683d88b a | |
3537 | -e81d457da15309b4fef4249aba9b50187999670d b | |
3538 | -c1536a972b9affea0f16e0680ba87332dc059146 c | |
3539 | -d96249ff5d57de5de093e6baff9e0aafa5276a74 d | |
3540 | ------------------------------------------------- | |
3541 | ||
3542 | NOTE: The commit object names shown above would be different for you, but they | |
3543 | should match the HEAD commit object names of your repositories. You can check | |
3544 | it by running `git ls-remote ../a`. | |
3545 | ||
3546 | Pulling down the submodules is a two-step process. First run `git submodule | |
3547 | init` to add the submodule repository URLs to `.git/config`: | |
3548 | ||
3549 | ------------------------------------------------- | |
3550 | $ git submodule init | |
3551 | ------------------------------------------------- | |
3552 | ||
6127c086 | 3553 | Now use `git submodule update` to clone the repositories and check out the |
38a457ba MV |
3554 | commits specified in the superproject: |
3555 | ||
3556 | ------------------------------------------------- | |
3557 | $ git submodule update | |
3558 | $ cd a | |
3559 | $ ls -a | |
3560 | . .. .git a.txt | |
3561 | ------------------------------------------------- | |
3562 | ||
6127c086 FC |
3563 | One major difference between `git submodule update` and `git submodule add` is |
3564 | that `git submodule update` checks out a specific commit, rather than the tip | |
38a457ba MV |
3565 | of a branch. It's like checking out a tag: the head is detached, so you're not |
3566 | working on a branch. | |
3567 | ||
3568 | ------------------------------------------------- | |
3569 | $ git branch | |
95f9be55 | 3570 | * (detached from d266b98) |
38a457ba MV |
3571 | master |
3572 | ------------------------------------------------- | |
3573 | ||
3574 | If you want to make a change within a submodule and you have a detached head, | |
3575 | then you should create or checkout a branch, make your changes, publish the | |
3576 | change within the submodule, and then update the superproject to reference the | |
3577 | new commit: | |
3578 | ||
3579 | ------------------------------------------------- | |
328c6cb8 | 3580 | $ git switch master |
38a457ba MV |
3581 | ------------------------------------------------- |
3582 | ||
3583 | or | |
3584 | ||
3585 | ------------------------------------------------- | |
328c6cb8 | 3586 | $ git switch -c fix-up |
38a457ba MV |
3587 | ------------------------------------------------- |
3588 | ||
3589 | then | |
3590 | ||
3591 | ------------------------------------------------- | |
3592 | $ echo "adding a line again" >> a.txt | |
3593 | $ git commit -a -m "Updated the submodule from within the superproject." | |
3594 | $ git push | |
3595 | $ cd .. | |
3596 | $ git diff | |
3597 | diff --git a/a b/a | |
3598 | index d266b98..261dfac 160000 | |
3599 | --- a/a | |
3600 | +++ b/a | |
3601 | @@ -1 +1 @@ | |
3602 | -Subproject commit d266b9873ad50488163457f025db7cdd9683d88b | |
3603 | +Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24 | |
3604 | $ git add a | |
3605 | $ git commit -m "Updated submodule a." | |
3606 | $ git push | |
3607 | ------------------------------------------------- | |
3608 | ||
3609 | You have to run `git submodule update` after `git pull` if you want to update | |
3610 | submodules, too. | |
3611 | ||
e79b3453 | 3612 | [[pitfalls-with-submodules]] |
fd5b820d | 3613 | === Pitfalls with submodules |
38a457ba MV |
3614 | |
3615 | Always publish the submodule change before publishing the change to the | |
3616 | superproject that references it. If you forget to publish the submodule change, | |
3617 | others won't be able to clone the repository: | |
3618 | ||
3619 | ------------------------------------------------- | |
3620 | $ cd ~/git/super/a | |
3621 | $ echo i added another line to this file >> a.txt | |
3622 | $ git commit -a -m "doing it wrong this time" | |
3623 | $ cd .. | |
3624 | $ git add a | |
3625 | $ git commit -m "Updated submodule a again." | |
3626 | $ git push | |
3627 | $ cd ~/git/cloned | |
3628 | $ git pull | |
3629 | $ git submodule update | |
3630 | error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git. | |
3631 | Did you forget to 'git add'? | |
3632 | Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a' | |
3633 | ------------------------------------------------- | |
3634 | ||
2de9b711 | 3635 | In older Git versions it could be easily forgotten to commit new or modified |
8d9e7d52 | 3636 | files in a submodule, which silently leads to similar problems as not pushing |
1249d8ad | 3637 | the submodule changes. Starting with Git 1.7.0 both `git status` and `git diff` |
8d9e7d52 | 3638 | in the superproject show submodules as modified when they contain new or |
1249d8ad TK |
3639 | modified files to protect against accidentally committing such a state. `git |
3640 | diff` will also add a `-dirty` to the work tree side when generating patch | |
3641 | output or used with the `--submodule` option: | |
8d9e7d52 JL |
3642 | |
3643 | ------------------------------------------------- | |
3644 | $ git diff | |
3645 | diff --git a/sub b/sub | |
3646 | --- a/sub | |
3647 | +++ b/sub | |
3648 | @@ -1 +1 @@ | |
3649 | -Subproject commit 3f356705649b5d566d97ff843cf193359229a453 | |
3650 | +Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty | |
3651 | $ git diff --submodule | |
3652 | Submodule sub 3f35670..3f35670-dirty: | |
3653 | ------------------------------------------------- | |
3654 | ||
38a457ba MV |
3655 | You also should not rewind branches in a submodule beyond commits that were |
3656 | ever recorded in any superproject. | |
3657 | ||
3658 | It's not safe to run `git submodule update` if you've made and committed | |
3659 | changes within a submodule without checking out a branch first. They will be | |
3660 | silently overwritten: | |
3661 | ||
3662 | ------------------------------------------------- | |
3663 | $ cat a.txt | |
3664 | module a | |
3665 | $ echo line added from private2 >> a.txt | |
3666 | $ git commit -a -m "line added inside private2" | |
3667 | $ cd .. | |
3668 | $ git submodule update | |
3669 | Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b' | |
3670 | $ cd a | |
3671 | $ cat a.txt | |
3672 | module a | |
3673 | ------------------------------------------------- | |
3674 | ||
3675 | NOTE: The changes are still visible in the submodule's reflog. | |
3676 | ||
91486733 TK |
3677 | If you have uncommitted changes in your submodule working tree, `git |
3678 | submodule update` will not overwrite them. Instead, you get the usual | |
3679 | warning about not being able switch from a dirty branch. | |
38a457ba | 3680 | |
1c6045ff | 3681 | [[low-level-operations]] |
fd5b820d | 3682 | == Low-level Git operations |
b181d57f | 3683 | |
1c6045ff | 3684 | Many of the higher-level commands were originally implemented as shell |
2de9b711 TA |
3685 | scripts using a smaller core of low-level Git commands. These can still |
3686 | be useful when doing unusual things with Git, or just as a way to | |
1c6045ff | 3687 | understand its inner workings. |
b181d57f | 3688 | |
1bbf1c79 | 3689 | [[object-manipulation]] |
fd5b820d | 3690 | === Object access and manipulation |
1bbf1c79 | 3691 | |
5162e697 DM |
3692 | The linkgit:git-cat-file[1] command can show the contents of any object, |
3693 | though the higher-level linkgit:git-show[1] is usually more useful. | |
1bbf1c79 | 3694 | |
5162e697 | 3695 | The linkgit:git-commit-tree[1] command allows constructing commits with |
1bbf1c79 BF |
3696 | arbitrary parents and trees. |
3697 | ||
5162e697 DM |
3698 | A tree can be created with linkgit:git-write-tree[1] and its data can be |
3699 | accessed by linkgit:git-ls-tree[1]. Two trees can be compared with | |
3700 | linkgit:git-diff-tree[1]. | |
1bbf1c79 | 3701 | |
5162e697 DM |
3702 | A tag is created with linkgit:git-mktag[1], and the signature can be |
3703 | verified by linkgit:git-verify-tag[1], though it is normally simpler to | |
3704 | use linkgit:git-tag[1] for both. | |
1bbf1c79 | 3705 | |
e34caace | 3706 | [[the-workflow]] |
fd5b820d | 3707 | === The Workflow |
b181d57f | 3708 | |
80f537f7 NTND |
3709 | High-level operations such as linkgit:git-commit[1] and |
3710 | linkgit:git-restore[1] work by moving data | |
06ada152 RW |
3711 | between the working tree, the index, and the object database. Git |
3712 | provides low-level operations which perform each of these steps | |
3713 | individually. | |
1c6045ff | 3714 | |
2de9b711 | 3715 | Generally, all Git operations work on the index file. Some operations |
b181d57f | 3716 | work *purely* on the index file (showing the current state of the |
1c6045ff BF |
3717 | index), but most operations move data between the index file and either |
3718 | the database or the working directory. Thus there are four main | |
3719 | combinations: | |
b181d57f | 3720 | |
e34caace | 3721 | [[working-directory-to-index]] |
fd5b820d | 3722 | ==== working directory -> index |
b181d57f | 3723 | |
5162e697 | 3724 | The linkgit:git-update-index[1] command updates the index with |
1c6045ff BF |
3725 | information from the working directory. You generally update the |
3726 | index information by just specifying the filename you want to update, | |
3727 | like so: | |
b181d57f BF |
3728 | |
3729 | ------------------------------------------------- | |
1c6045ff | 3730 | $ git update-index filename |
b181d57f BF |
3731 | ------------------------------------------------- |
3732 | ||
5fe8f49b | 3733 | but to avoid common mistakes with filename globbing etc., the command |
b181d57f BF |
3734 | will not normally add totally new entries or remove old entries, |
3735 | i.e. it will normally just update existing cache entries. | |
3736 | ||
2de9b711 | 3737 | To tell Git that yes, you really do realize that certain files no |
b181d57f BF |
3738 | longer exist, or that new files should be added, you |
3739 | should use the `--remove` and `--add` flags respectively. | |
3740 | ||
3741 | NOTE! A `--remove` flag does 'not' mean that subsequent filenames will | |
3742 | necessarily be removed: if the files still exist in your directory | |
3743 | structure, the index will be updated with their new status, not | |
10455d2a | 3744 | removed. The only thing `--remove` means is that update-index will be |
b181d57f BF |
3745 | considering a removed file to be a valid thing, and if the file really |
3746 | does not exist any more, it will update the index accordingly. | |
3747 | ||
467c0197 | 3748 | As a special case, you can also do `git update-index --refresh`, which |
b181d57f BF |
3749 | will refresh the "stat" information of each index to match the current |
3750 | stat information. It will 'not' update the object status itself, and | |
3751 | it will only update the fields that are used to quickly test whether | |
3752 | an object still matches its old backing store object. | |
3753 | ||
5162e697 DM |
3754 | The previously introduced linkgit:git-add[1] is just a wrapper for |
3755 | linkgit:git-update-index[1]. | |
1c6045ff | 3756 | |
e34caace | 3757 | [[index-to-object-database]] |
fd5b820d | 3758 | ==== index -> object database |
b181d57f BF |
3759 | |
3760 | You write your current index file to a "tree" object with the program | |
3761 | ||
3762 | ------------------------------------------------- | |
1c6045ff | 3763 | $ git write-tree |
b181d57f BF |
3764 | ------------------------------------------------- |
3765 | ||
2ef8ac1b | 3766 | that doesn't come with any options--it will just write out the |
b181d57f BF |
3767 | current index into the set of tree objects that describe that state, |
3768 | and it will return the name of the resulting top-level tree. You can | |
3769 | use that tree to re-generate the index at any time by going in the | |
3770 | other direction: | |
3771 | ||
e34caace | 3772 | [[object-database-to-index]] |
fd5b820d | 3773 | ==== object database -> index |
b181d57f BF |
3774 | |
3775 | You read a "tree" file from the object database, and use that to | |
2ef8ac1b | 3776 | populate (and overwrite--don't do this if your index contains any |
b181d57f BF |
3777 | unsaved state that you might want to restore later!) your current |
3778 | index. Normal operation is just | |
3779 | ||
3780 | ------------------------------------------------- | |
a6e5ef7d | 3781 | $ git read-tree <SHA-1 of tree> |
b181d57f BF |
3782 | ------------------------------------------------- |
3783 | ||
3784 | and your index file will now be equivalent to the tree that you saved | |
3785 | earlier. However, that is only your 'index' file: your working | |
3786 | directory contents have not been modified. | |
3787 | ||
e34caace | 3788 | [[index-to-working-directory]] |
fd5b820d | 3789 | ==== index -> working directory |
b181d57f BF |
3790 | |
3791 | You update your working directory from the index by "checking out" | |
3792 | files. This is not a very common operation, since normally you'd just | |
3793 | keep your files updated, and rather than write to your working | |
3794 | directory, you'd tell the index files about the changes in your | |
6127c086 | 3795 | working directory (i.e. `git update-index`). |
b181d57f BF |
3796 | |
3797 | However, if you decide to jump to a new version, or check out somebody | |
3798 | else's version, or just restore a previous tree, you'd populate your | |
3799 | index file with read-tree, and then you need to check out the result | |
3800 | with | |
3801 | ||
3802 | ------------------------------------------------- | |
b1889c36 | 3803 | $ git checkout-index filename |
b181d57f BF |
3804 | ------------------------------------------------- |
3805 | ||
3806 | or, if you want to check out all of the index, use `-a`. | |
3807 | ||
6127c086 | 3808 | NOTE! `git checkout-index` normally refuses to overwrite old files, so |
b181d57f | 3809 | if you have an old version of the tree already checked out, you will |
1249d8ad | 3810 | need to use the `-f` flag ('before' the `-a` flag or the filename) to |
b181d57f BF |
3811 | 'force' the checkout. |
3812 | ||
3813 | ||
3814 | Finally, there are a few odds and ends which are not purely moving | |
3815 | from one representation to the other: | |
3816 | ||
e34caace | 3817 | [[tying-it-all-together]] |
fd5b820d | 3818 | ==== Tying it all together |
b181d57f | 3819 | |
1249d8ad | 3820 | To commit a tree you have instantiated with `git write-tree`, you'd |
b181d57f | 3821 | create a "commit" object that refers to that tree and the history |
2ef8ac1b | 3822 | behind it--most notably the "parent" commits that preceded it in |
b181d57f BF |
3823 | history. |
3824 | ||
3825 | Normally a "commit" has one parent: the previous state of the tree | |
3826 | before a certain change was made. However, sometimes it can have two | |
3827 | or more parent commits, in which case we call it a "merge", due to the | |
3828 | fact that such a commit brings together ("merges") two or more | |
3829 | previous states represented by other commits. | |
3830 | ||
3831 | In other words, while a "tree" represents a particular directory state | |
ddd4ddef | 3832 | of a working directory, a "commit" represents that state in time, |
b181d57f BF |
3833 | and explains how we got there. |
3834 | ||
3835 | You create a commit object by giving it the tree that describes the | |
3836 | state at the time of the commit, and a list of parents: | |
3837 | ||
3838 | ------------------------------------------------- | |
0adda936 | 3839 | $ git commit-tree <tree> -p <parent> [(-p <parent2>)...] |
b181d57f BF |
3840 | ------------------------------------------------- |
3841 | ||
3842 | and then giving the reason for the commit on stdin (either through | |
3843 | redirection from a pipe or file, or by just typing it at the tty). | |
3844 | ||
6127c086 | 3845 | `git commit-tree` will return the name of the object that represents |
b181d57f | 3846 | that commit, and you should save it away for later use. Normally, |
2de9b711 | 3847 | you'd commit a new `HEAD` state, and while Git doesn't care where you |
b181d57f BF |
3848 | save the note about that state, in practice we tend to just write the |
3849 | result to the file pointed at by `.git/HEAD`, so that we can always see | |
3850 | what the last committed state was. | |
3851 | ||
381183fb | 3852 | Here is a picture that illustrates how various pieces fit together: |
b181d57f BF |
3853 | |
3854 | ------------ | |
3855 | ||
3856 | commit-tree | |
3857 | commit obj | |
3858 | +----+ | |
3859 | | | | |
3860 | | | | |
3861 | V V | |
3862 | +-----------+ | |
3863 | | Object DB | | |
3864 | | Backing | | |
3865 | | Store | | |
3866 | +-----------+ | |
3867 | ^ | |
3868 | write-tree | | | |
3869 | tree obj | | | |
3870 | | | read-tree | |
3871 | | | tree obj | |
3872 | V | |
3873 | +-----------+ | |
3874 | | Index | | |
3875 | | "cache" | | |
3876 | +-----------+ | |
3877 | update-index ^ | |
3878 | blob obj | | | |
3879 | | | | |
3880 | checkout-index -u | | checkout-index | |
3881 | stat | | blob obj | |
3882 | V | |
3883 | +-----------+ | |
3884 | | Working | | |
3885 | | Directory | | |
3886 | +-----------+ | |
3887 | ||
3888 | ------------ | |
3889 | ||
3890 | ||
e34caace | 3891 | [[examining-the-data]] |
fd5b820d | 3892 | === Examining the data |
b181d57f BF |
3893 | |
3894 | You can examine the data represented in the object database and the | |
3895 | index with various helper tools. For every object, you can use | |
5162e697 | 3896 | linkgit:git-cat-file[1] to examine details about the |
b181d57f BF |
3897 | object: |
3898 | ||
3899 | ------------------------------------------------- | |
b1889c36 | 3900 | $ git cat-file -t <objectname> |
b181d57f BF |
3901 | ------------------------------------------------- |
3902 | ||
3903 | shows the type of the object, and once you have the type (which is | |
3904 | usually implicit in where you find the object), you can use | |
3905 | ||
3906 | ------------------------------------------------- | |
b1889c36 | 3907 | $ git cat-file blob|tree|commit|tag <objectname> |
b181d57f BF |
3908 | ------------------------------------------------- |
3909 | ||
3910 | to show its contents. NOTE! Trees have binary content, and as a result | |
3911 | there is a special helper for showing that content, called | |
6127c086 | 3912 | `git ls-tree`, which turns the binary content into a more easily |
b181d57f BF |
3913 | readable form. |
3914 | ||
3915 | It's especially instructive to look at "commit" objects, since those | |
3916 | tend to be small and fairly self-explanatory. In particular, if you | |
3917 | follow the convention of having the top commit name in `.git/HEAD`, | |
3918 | you can do | |
3919 | ||
3920 | ------------------------------------------------- | |
b1889c36 | 3921 | $ git cat-file commit HEAD |
b181d57f BF |
3922 | ------------------------------------------------- |
3923 | ||
3924 | to see what the top commit was. | |
3925 | ||
e34caace | 3926 | [[merging-multiple-trees]] |
fd5b820d | 3927 | === Merging multiple trees |
d19fbc3c | 3928 | |
e8e9964d TA |
3929 | Git can help you perform a three-way merge, which can in turn be |
3930 | used for a many-way merge by repeating the merge procedure several | |
3931 | times. The usual situation is that you only do one three-way merge | |
3932 | (reconciling two lines of history) and commit the result, but if | |
3933 | you like to, you can merge several branches in one go. | |
b181d57f | 3934 | |
e8e9964d TA |
3935 | To perform a three-way merge, you start with the two commits you |
3936 | want to merge, find their closest common parent (a third commit), | |
3937 | and compare the trees corresponding to these three commits. | |
b181d57f | 3938 | |
e8e9964d TA |
3939 | To get the "base" for the merge, look up the common parent of two |
3940 | commits: | |
b181d57f BF |
3941 | |
3942 | ------------------------------------------------- | |
b1889c36 | 3943 | $ git merge-base <commit1> <commit2> |
b181d57f BF |
3944 | ------------------------------------------------- |
3945 | ||
e8e9964d TA |
3946 | This prints the name of a commit they are both based on. You should |
3947 | now look up the tree objects of those commits, which you can easily | |
3948 | do with | |
b181d57f BF |
3949 | |
3950 | ------------------------------------------------- | |
b1889c36 | 3951 | $ git cat-file commit <commitname> | head -1 |
b181d57f BF |
3952 | ------------------------------------------------- |
3953 | ||
3954 | since the tree object information is always the first line in a commit | |
3955 | object. | |
3956 | ||
1191ee18 | 3957 | Once you know the three trees you are going to merge (the one "original" |
c64415e2 | 3958 | tree, aka the common tree, and the two "result" trees, aka the branches |
1191ee18 BF |
3959 | you want to merge), you do a "merge" read into the index. This will |
3960 | complain if it has to throw away your old index contents, so you should | |
2ef8ac1b | 3961 | make sure that you've committed those--in fact you would normally |
1191ee18 BF |
3962 | always do a merge against your last commit (which should thus match what |
3963 | you have in your current index anyway). | |
b181d57f BF |
3964 | |
3965 | To do the merge, do | |
3966 | ||
3967 | ------------------------------------------------- | |
b1889c36 | 3968 | $ git read-tree -m -u <origtree> <yourtree> <targettree> |
b181d57f BF |
3969 | ------------------------------------------------- |
3970 | ||
3971 | which will do all trivial merge operations for you directly in the | |
3972 | index file, and you can just write the result out with | |
467c0197 | 3973 | `git write-tree`. |
b181d57f BF |
3974 | |
3975 | ||
e34caace | 3976 | [[merging-multiple-trees-2]] |
fd5b820d | 3977 | === Merging multiple trees, continued |
b181d57f BF |
3978 | |
3979 | Sadly, many merges aren't trivial. If there are files that have | |
06ada152 | 3980 | been added, moved or removed, or if both branches have modified the |
b181d57f BF |
3981 | same file, you will be left with an index tree that contains "merge |
3982 | entries" in it. Such an index tree can 'NOT' be written out to a tree | |
3983 | object, and you will have to resolve any such merge clashes using | |
3984 | other tools before you can write out the result. | |
3985 | ||
b1889c36 | 3986 | You can examine such index state with `git ls-files --unmerged` |
b181d57f BF |
3987 | command. An example: |
3988 | ||
3989 | ------------------------------------------------ | |
b1889c36 JN |
3990 | $ git read-tree -m $orig HEAD $target |
3991 | $ git ls-files --unmerged | |
b181d57f BF |
3992 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c |
3993 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c | |
3994 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c | |
3995 | ------------------------------------------------ | |
3996 | ||
b1889c36 | 3997 | Each line of the `git ls-files --unmerged` output begins with |
a6e5ef7d | 3998 | the blob mode bits, blob SHA-1, 'stage number', and the |
2de9b711 | 3999 | filename. The 'stage number' is Git's way to say which tree it |
edfbbf7e ŠN |
4000 | came from: stage 1 corresponds to the `$orig` tree, stage 2 to |
4001 | the `HEAD` tree, and stage 3 to the `$target` tree. | |
b181d57f BF |
4002 | |
4003 | Earlier we said that trivial merges are done inside | |
6127c086 | 4004 | `git read-tree -m`. For example, if the file did not change |
a58088ab | 4005 | from `$orig` to `HEAD` or `$target`, or if the file changed |
b181d57f BF |
4006 | from `$orig` to `HEAD` and `$orig` to `$target` the same way, |
4007 | obviously the final outcome is what is in `HEAD`. What the | |
4008 | above example shows is that file `hello.c` was changed from | |
4009 | `$orig` to `HEAD` and `$orig` to `$target` in a different way. | |
4010 | You could resolve this by running your favorite 3-way merge | |
2de9b711 | 4011 | program, e.g. `diff3`, `merge`, or Git's own merge-file, on |
c64415e2 | 4012 | the blob objects from these three stages yourself, like this: |
b181d57f BF |
4013 | |
4014 | ------------------------------------------------ | |
f61d89e1 AR |
4015 | $ git cat-file blob 263414f >hello.c~1 |
4016 | $ git cat-file blob 06fa6a2 >hello.c~2 | |
4017 | $ git cat-file blob cc44c73 >hello.c~3 | |
c64415e2 | 4018 | $ git merge-file hello.c~2 hello.c~1 hello.c~3 |
b181d57f BF |
4019 | ------------------------------------------------ |
4020 | ||
4021 | This would leave the merge result in `hello.c~2` file, along | |
4022 | with conflict markers if there are conflicts. After verifying | |
2de9b711 | 4023 | the merge result makes sense, you can tell Git what the final |
b181d57f BF |
4024 | merge result for this file is by: |
4025 | ||
4026 | ------------------------------------------------- | |
4027 | $ mv -f hello.c~2 hello.c | |
b1889c36 | 4028 | $ git update-index hello.c |
b181d57f BF |
4029 | ------------------------------------------------- |
4030 | ||
6127c086 | 4031 | When a path is in the "unmerged" state, running `git update-index` for |
2de9b711 | 4032 | that path tells Git to mark the path resolved. |
b181d57f | 4033 | |
2de9b711 | 4034 | The above is the description of a Git merge at the lowest level, |
b181d57f | 4035 | to help you understand what conceptually happens under the hood. |
2de9b711 | 4036 | In practice, nobody, not even Git itself, runs `git cat-file` three times |
6127c086 | 4037 | for this. There is a `git merge-index` program that extracts the |
b181d57f BF |
4038 | stages to temporary files and calls a "merge" script on it: |
4039 | ||
4040 | ------------------------------------------------- | |
b1889c36 | 4041 | $ git merge-index git-merge-one-file hello.c |
b181d57f BF |
4042 | ------------------------------------------------- |
4043 | ||
6127c086 | 4044 | and that is what higher level `git merge -s resolve` is implemented with. |
b181d57f | 4045 | |
971aa71f | 4046 | [[hacking-git]] |
fd5b820d | 4047 | == Hacking Git |
971aa71f | 4048 | |
2de9b711 TA |
4049 | This chapter covers internal details of the Git implementation which |
4050 | probably only Git developers need to understand. | |
971aa71f | 4051 | |
f2327c6c | 4052 | [[object-details]] |
fd5b820d | 4053 | === Object storage format |
f2327c6c BF |
4054 | |
4055 | All objects have a statically determined "type" which identifies the | |
4056 | format of the object (i.e. how it is used, and how it can refer to other | |
4057 | objects). There are currently four different object types: "blob", | |
4058 | "tree", "commit", and "tag". | |
4059 | ||
4060 | Regardless of object type, all objects share the following | |
4061 | characteristics: they are all deflated with zlib, and have a header | |
4062 | that not only specifies their type, but also provides size information | |
a6e5ef7d | 4063 | about the data in the object. It's worth noting that the SHA-1 hash |
f2327c6c BF |
4064 | that is used to name the object is the hash of the original data |
4065 | plus this header, so `sha1sum` 'file' does not match the object name | |
4066 | for 'file'. | |
f2327c6c BF |
4067 | |
4068 | As a result, the general consistency of an object can always be tested | |
4069 | independently of the contents or the type of the object: all objects can | |
4070 | be validated by verifying that (a) their hashes match the content of the | |
4071 | file and (b) the object successfully inflates to a stream of bytes that | |
1249d8ad TK |
4072 | forms a sequence of |
4073 | `<ascii type without space> + <space> + <ascii decimal size> + | |
4074 | <byte\0> + <binary object data>`. | |
f2327c6c BF |
4075 | |
4076 | The structured objects can further have their structure and | |
4077 | connectivity to other objects verified. This is generally done with | |
6127c086 | 4078 | the `git fsck` program, which generates a full dependency graph |
f2327c6c BF |
4079 | of all objects, and verifies their internal consistency (in addition |
4080 | to just verifying their superficial consistency through the hash). | |
4081 | ||
126640af | 4082 | [[birdview-on-the-source-code]] |
fd5b820d | 4083 | === A birds-eye view of Git's source code |
126640af | 4084 | |
a5fc33b4 BF |
4085 | It is not always easy for new developers to find their way through Git's |
4086 | source code. This section gives you a little guidance to show where to | |
4087 | start. | |
126640af | 4088 | |
a5fc33b4 | 4089 | A good place to start is with the contents of the initial commit, with: |
126640af JS |
4090 | |
4091 | ---------------------------------------------------- | |
328c6cb8 | 4092 | $ git switch --detach e83c5163 |
126640af JS |
4093 | ---------------------------------------------------- |
4094 | ||
2de9b711 | 4095 | The initial revision lays the foundation for almost everything Git has |
a5fc33b4 | 4096 | today, but is small enough to read in one sitting. |
126640af | 4097 | |
a5fc33b4 BF |
4098 | Note that terminology has changed since that revision. For example, the |
4099 | README in that revision uses the word "changeset" to describe what we | |
4100 | now call a <<def_commit_object,commit>>. | |
126640af | 4101 | |
843c81dc | 4102 | Also, we do not call it "cache" any more, but rather "index"; however, the |
126640af JS |
4103 | file is still called `cache.h`. Remark: Not much reason to change it now, |
4104 | especially since there is no good single name for it anyway, because it is | |
4105 | basically _the_ header file which is included by _all_ of Git's C sources. | |
4106 | ||
a5fc33b4 BF |
4107 | If you grasp the ideas in that initial commit, you should check out a |
4108 | more recent version and skim `cache.h`, `object.h` and `commit.h`. | |
126640af JS |
4109 | |
4110 | In the early days, Git (in the tradition of UNIX) was a bunch of programs | |
4111 | which were extremely simple, and which you used in scripts, piping the | |
4112 | output of one into another. This turned out to be good for initial | |
4113 | development, since it was easier to test new things. However, recently | |
4114 | many of these parts have become builtins, and some of the core has been | |
4115 | "libified", i.e. put into libgit.a for performance, portability reasons, | |
4116 | and to avoid code duplication. | |
4117 | ||
4118 | By now, you know what the index is (and find the corresponding data | |
4119 | structures in `cache.h`), and that there are just a couple of object types | |
4120 | (blobs, trees, commits and tags) which inherit their common structure from | |
4121 | `struct object`, which is their first member (and thus, you can cast e.g. | |
4122 | `(struct object *)commit` to achieve the _same_ as `&commit->object`, i.e. | |
4123 | get at the object name and flags). | |
4124 | ||
4125 | Now is a good point to take a break to let this information sink in. | |
4126 | ||
4127 | Next step: get familiar with the object naming. Read <<naming-commits>>. | |
4128 | There are quite a few ways to name an object (and not only revisions!). | |
4129 | All of these are handled in `sha1_name.c`. Just have a quick look at | |
4130 | the function `get_sha1()`. A lot of the special handling is done by | |
4131 | functions like `get_sha1_basic()` or the likes. | |
4132 | ||
4133 | This is just to get you into the groove for the most libified part of Git: | |
4134 | the revision walker. | |
4135 | ||
6127c086 | 4136 | Basically, the initial version of `git log` was a shell script: |
126640af JS |
4137 | |
4138 | ---------------------------------------------------------------- | |
4139 | $ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \ | |
4140 | LESS=-S ${PAGER:-less} | |
4141 | ---------------------------------------------------------------- | |
4142 | ||
4143 | What does this mean? | |
4144 | ||
6127c086 | 4145 | `git rev-list` is the original version of the revision walker, which |
126640af | 4146 | _always_ printed a list of revisions to stdout. It is still functional, |
57f6ec02 | 4147 | and needs to, since most new Git commands start out as scripts using |
6127c086 | 4148 | `git rev-list`. |
126640af | 4149 | |
6127c086 | 4150 | `git rev-parse` is not as important any more; it was only used to filter out |
126640af JS |
4151 | options that were relevant for the different plumbing commands that were |
4152 | called by the script. | |
4153 | ||
6127c086 | 4154 | Most of what `git rev-list` did is contained in `revision.c` and |
126640af JS |
4155 | `revision.h`. It wraps the options in a struct named `rev_info`, which |
4156 | controls how and what revisions are walked, and more. | |
4157 | ||
6127c086 | 4158 | The original job of `git rev-parse` is now taken by the function |
06ab60c0 | 4159 | `setup_revisions()`, which parses the revisions and the common command-line |
126640af | 4160 | options for the revision walker. This information is stored in the struct |
06ab60c0 | 4161 | `rev_info` for later consumption. You can do your own command-line option |
126640af JS |
4162 | parsing after calling `setup_revisions()`. After that, you have to call |
4163 | `prepare_revision_walk()` for initialization, and then you can get the | |
4164 | commits one by one with the function `get_revision()`. | |
4165 | ||
4166 | If you are interested in more details of the revision walking process, | |
4167 | just have a look at the first implementation of `cmd_log()`; call | |
6cf378f0 | 4168 | `git show v1.3.0~155^2~4` and scroll down to that function (note that you |
126640af JS |
4169 | no longer need to call `setup_pager()` directly). |
4170 | ||
6127c086 | 4171 | Nowadays, `git log` is a builtin, which means that it is _contained_ in the |
126640af JS |
4172 | command `git`. The source side of a builtin is |
4173 | ||
09b7e220 PH |
4174 | - a function called `cmd_<bla>`, typically defined in `builtin/<bla.c>` |
4175 | (note that older versions of Git used to have it in `builtin-<bla>.c` | |
4176 | instead), and declared in `builtin.h`. | |
126640af JS |
4177 | |
4178 | - an entry in the `commands[]` array in `git.c`, and | |
4179 | ||
4180 | - an entry in `BUILTIN_OBJECTS` in the `Makefile`. | |
4181 | ||
4182 | Sometimes, more than one builtin is contained in one source file. For | |
09b7e220 | 4183 | example, `cmd_whatchanged()` and `cmd_log()` both reside in `builtin/log.c`, |
126640af JS |
4184 | since they share quite a bit of code. In that case, the commands which are |
4185 | _not_ named like the `.c` file in which they live have to be listed in | |
4186 | `BUILT_INS` in the `Makefile`. | |
4187 | ||
6127c086 | 4188 | `git log` looks more complicated in C than it does in the original script, |
126640af JS |
4189 | but that allows for a much greater flexibility and performance. |
4190 | ||
4191 | Here again it is a good point to take a pause. | |
4192 | ||
4193 | Lesson three is: study the code. Really, it is the best way to learn about | |
4194 | the organization of Git (after you know the basic concepts). | |
4195 | ||
4196 | So, think about something which you are interested in, say, "how can I | |
4197 | access a blob just knowing the object name of it?". The first step is to | |
4198 | find a Git command with which you can do it. In this example, it is either | |
6127c086 | 4199 | `git show` or `git cat-file`. |
126640af | 4200 | |
6127c086 | 4201 | For the sake of clarity, let's stay with `git cat-file`, because it |
126640af JS |
4202 | |
4203 | - is plumbing, and | |
4204 | ||
4205 | - was around even in the initial commit (it literally went only through | |
09b7e220 | 4206 | some 20 revisions as `cat-file.c`, was renamed to `builtin/cat-file.c` |
126640af JS |
4207 | when made a builtin, and then saw less than 10 versions). |
4208 | ||
09b7e220 | 4209 | So, look into `builtin/cat-file.c`, search for `cmd_cat_file()` and look what |
126640af JS |
4210 | it does. |
4211 | ||
4212 | ------------------------------------------------------------------ | |
4213 | git_config(git_default_config); | |
4214 | if (argc != 3) | |
6127c086 | 4215 | usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>"); |
126640af JS |
4216 | if (get_sha1(argv[2], sha1)) |
4217 | die("Not a valid object name %s", argv[2]); | |
4218 | ------------------------------------------------------------------ | |
4219 | ||
4220 | Let's skip over the obvious details; the only really interesting part | |
4221 | here is the call to `get_sha1()`. It tries to interpret `argv[2]` as an | |
4222 | object name, and if it refers to an object which is present in the current | |
4223 | repository, it writes the resulting SHA-1 into the variable `sha1`. | |
4224 | ||
4225 | Two things are interesting here: | |
4226 | ||
4227 | - `get_sha1()` returns 0 on _success_. This might surprise some new | |
4228 | Git hackers, but there is a long tradition in UNIX to return different | |
2ef8ac1b | 4229 | negative numbers in case of different errors--and 0 on success. |
126640af JS |
4230 | |
4231 | - the variable `sha1` in the function signature of `get_sha1()` is `unsigned | |
6cf378f0 | 4232 | char *`, but is actually expected to be a pointer to `unsigned |
126640af | 4233 | char[20]`. This variable will contain the 160-bit SHA-1 of the given |
6cf378f0 | 4234 | commit. Note that whenever a SHA-1 is passed as `unsigned char *`, it |
126640af | 4235 | is the binary representation, as opposed to the ASCII representation in |
a5fc33b4 | 4236 | hex characters, which is passed as `char *`. |
126640af JS |
4237 | |
4238 | You will see both of these things throughout the code. | |
4239 | ||
4240 | Now, for the meat: | |
4241 | ||
4242 | ----------------------------------------------------------------------------- | |
4243 | case 0: | |
4244 | buf = read_object_with_reference(sha1, argv[1], &size, NULL); | |
4245 | ----------------------------------------------------------------------------- | |
4246 | ||
4247 | This is how you read a blob (actually, not only a blob, but any type of | |
4248 | object). To know how the function `read_object_with_reference()` actually | |
4249 | works, find the source code for it (something like `git grep | |
2de9b711 | 4250 | read_object_with | grep ":[a-z]"` in the Git repository), and read |
126640af JS |
4251 | the source. |
4252 | ||
4253 | To find out how the result can be used, just read on in `cmd_cat_file()`: | |
4254 | ||
4255 | ----------------------------------- | |
4256 | write_or_die(1, buf, size); | |
4257 | ----------------------------------- | |
4258 | ||
4259 | Sometimes, you do not know where to look for a feature. In many such cases, | |
6127c086 | 4260 | it helps to search through the output of `git log`, and then `git show` the |
126640af JS |
4261 | corresponding commit. |
4262 | ||
6127c086 | 4263 | Example: If you know that there was some test case for `git bundle`, but |
126640af JS |
4264 | do not remember where it was (yes, you _could_ `git grep bundle t/`, but that |
4265 | does not illustrate the point!): | |
4266 | ||
4267 | ------------------------ | |
4268 | $ git log --no-merges t/ | |
4269 | ------------------------ | |
4270 | ||
4271 | In the pager (`less`), just search for "bundle", go a few lines back, | |
f61d89e1 | 4272 | and see that it is in commit 18449ab0. Now just copy this object name, |
126640af JS |
4273 | and paste it into the command line |
4274 | ||
4275 | ------------------- | |
4276 | $ git show 18449ab0 | |
4277 | ------------------- | |
4278 | ||
4279 | Voila. | |
4280 | ||
4281 | Another example: Find out what to do in order to make some script a | |
4282 | builtin: | |
4283 | ||
4284 | ------------------------------------------------- | |
09b7e220 | 4285 | $ git log --no-merges --diff-filter=A builtin/*.c |
126640af JS |
4286 | ------------------------------------------------- |
4287 | ||
4288 | You see, Git is actually the best tool to find out about the source of Git | |
4289 | itself! | |
4290 | ||
e34caace | 4291 | [[glossary]] |
fd5b820d | 4292 | == Git Glossary |
497c8331 | 4293 | |
03920ac6 | 4294 | [[git-explained]] |
fd5b820d | 4295 | === Git explained |
03920ac6 | 4296 | |
497c8331 | 4297 | include::glossary-content.txt[] |
d19fbc3c | 4298 | |
2624d9a5 | 4299 | [[git-quick-start]] |
fd5b820d MÅ |
4300 | [appendix] |
4301 | == Git Quick Reference | |
2624d9a5 | 4302 | |
99f171bb BF |
4303 | This is a quick summary of the major commands; the previous chapters |
4304 | explain how these work in more detail. | |
2624d9a5 BF |
4305 | |
4306 | [[quick-creating-a-new-repository]] | |
fd5b820d | 4307 | === Creating a new repository |
2624d9a5 BF |
4308 | |
4309 | From a tarball: | |
4310 | ||
4311 | ----------------------------------------------- | |
4312 | $ tar xzf project.tar.gz | |
4313 | $ cd project | |
4314 | $ git init | |
4315 | Initialized empty Git repository in .git/ | |
4316 | $ git add . | |
4317 | $ git commit | |
4318 | ----------------------------------------------- | |
4319 | ||
4320 | From a remote repository: | |
4321 | ||
4322 | ----------------------------------------------- | |
4323 | $ git clone git://example.com/pub/project.git | |
4324 | $ cd project | |
4325 | ----------------------------------------------- | |
4326 | ||
4327 | [[managing-branches]] | |
fd5b820d | 4328 | === Managing branches |
2624d9a5 BF |
4329 | |
4330 | ----------------------------------------------- | |
328c6cb8 NTND |
4331 | $ git branch # list all local branches in this repo |
4332 | $ git switch test # switch working directory to branch "test" | |
4333 | $ git branch new # create branch "new" starting at current HEAD | |
4334 | $ git branch -d new # delete branch "new" | |
2624d9a5 BF |
4335 | ----------------------------------------------- |
4336 | ||
06ada152 | 4337 | Instead of basing a new branch on current HEAD (the default), use: |
2624d9a5 BF |
4338 | |
4339 | ----------------------------------------------- | |
4340 | $ git branch new test # branch named "test" | |
4341 | $ git branch new v2.6.15 # tag named v2.6.15 | |
4342 | $ git branch new HEAD^ # commit before the most recent | |
4343 | $ git branch new HEAD^^ # commit before that | |
4344 | $ git branch new test~10 # ten commits before tip of branch "test" | |
4345 | ----------------------------------------------- | |
4346 | ||
4347 | Create and switch to a new branch at the same time: | |
4348 | ||
4349 | ----------------------------------------------- | |
328c6cb8 | 4350 | $ git switch -c new v2.6.15 |
2624d9a5 BF |
4351 | ----------------------------------------------- |
4352 | ||
4353 | Update and examine branches from the repository you cloned from: | |
4354 | ||
4355 | ----------------------------------------------- | |
4356 | $ git fetch # update | |
4357 | $ git branch -r # list | |
4358 | origin/master | |
4359 | origin/next | |
4360 | ... | |
328c6cb8 | 4361 | $ git switch -c masterwork origin/master |
2624d9a5 BF |
4362 | ----------------------------------------------- |
4363 | ||
4364 | Fetch a branch from a different repository, and give it a new | |
4365 | name in your repository: | |
4366 | ||
4367 | ----------------------------------------------- | |
4368 | $ git fetch git://example.com/project.git theirbranch:mybranch | |
4369 | $ git fetch git://example.com/project.git v2.6.15:mybranch | |
4370 | ----------------------------------------------- | |
4371 | ||
4372 | Keep a list of repositories you work with regularly: | |
4373 | ||
4374 | ----------------------------------------------- | |
4375 | $ git remote add example git://example.com/project.git | |
4376 | $ git remote # list remote repositories | |
4377 | example | |
4378 | origin | |
4379 | $ git remote show example # get details | |
4380 | * remote example | |
4381 | URL: git://example.com/project.git | |
4382 | Tracked remote branches | |
20244ea2 JS |
4383 | master |
4384 | next | |
4385 | ... | |
2624d9a5 BF |
4386 | $ git fetch example # update branches from example |
4387 | $ git branch -r # list all remote branches | |
4388 | ----------------------------------------------- | |
4389 | ||
4390 | ||
4391 | [[exploring-history]] | |
fd5b820d | 4392 | === Exploring history |
2624d9a5 BF |
4393 | |
4394 | ----------------------------------------------- | |
4395 | $ gitk # visualize and browse history | |
4396 | $ git log # list all commits | |
4397 | $ git log src/ # ...modifying src/ | |
4398 | $ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15 | |
4399 | $ git log master..test # ...in branch test, not in branch master | |
4400 | $ git log test..master # ...in branch master, but not in test | |
4401 | $ git log test...master # ...in one branch, not in both | |
4402 | $ git log -S'foo()' # ...where difference contain "foo()" | |
4403 | $ git log --since="2 weeks ago" | |
4404 | $ git log -p # show patches as well | |
4405 | $ git show # most recent commit | |
4406 | $ git diff v2.6.15..v2.6.16 # diff between two tagged versions | |
4407 | $ git diff v2.6.15..HEAD # diff with current head | |
4408 | $ git grep "foo()" # search working directory for "foo()" | |
4409 | $ git grep v2.6.15 "foo()" # search old tree for "foo()" | |
4410 | $ git show v2.6.15:a.txt # look at old version of a.txt | |
4411 | ----------------------------------------------- | |
4412 | ||
4413 | Search for regressions: | |
4414 | ||
4415 | ----------------------------------------------- | |
4416 | $ git bisect start | |
4417 | $ git bisect bad # current version is bad | |
4418 | $ git bisect good v2.6.13-rc2 # last known good revision | |
4419 | Bisecting: 675 revisions left to test after this | |
4420 | # test here, then: | |
4421 | $ git bisect good # if this revision is good, or | |
4422 | $ git bisect bad # if this revision is bad. | |
4423 | # repeat until done. | |
4424 | ----------------------------------------------- | |
4425 | ||
4426 | [[making-changes]] | |
fd5b820d | 4427 | === Making changes |
2624d9a5 | 4428 | |
2de9b711 | 4429 | Make sure Git knows who to blame: |
2624d9a5 BF |
4430 | |
4431 | ------------------------------------------------ | |
4432 | $ cat >>~/.gitconfig <<\EOF | |
4433 | [user] | |
4434 | name = Your Name Comes Here | |
4435 | email = you@yourdomain.example.com | |
4436 | EOF | |
4437 | ------------------------------------------------ | |
4438 | ||
4439 | Select file contents to include in the next commit, then make the | |
4440 | commit: | |
4441 | ||
4442 | ----------------------------------------------- | |
4443 | $ git add a.txt # updated file | |
4444 | $ git add b.txt # new file | |
4445 | $ git rm c.txt # old file | |
4446 | $ git commit | |
4447 | ----------------------------------------------- | |
4448 | ||
4449 | Or, prepare and create the commit in one step: | |
4450 | ||
4451 | ----------------------------------------------- | |
4452 | $ git commit d.txt # use latest content only of d.txt | |
4453 | $ git commit -a # use latest content of all tracked files | |
4454 | ----------------------------------------------- | |
4455 | ||
4456 | [[merging]] | |
fd5b820d | 4457 | === Merging |
2624d9a5 BF |
4458 | |
4459 | ----------------------------------------------- | |
4460 | $ git merge test # merge branch "test" into the current branch | |
4461 | $ git pull git://example.com/project.git master | |
4462 | # fetch and merge in remote branch | |
4463 | $ git pull . test # equivalent to git merge test | |
4464 | ----------------------------------------------- | |
4465 | ||
4466 | [[sharing-your-changes]] | |
fd5b820d | 4467 | === Sharing your changes |
2624d9a5 BF |
4468 | |
4469 | Importing or exporting patches: | |
4470 | ||
4471 | ----------------------------------------------- | |
4472 | $ git format-patch origin..HEAD # format a patch for each commit | |
4473 | # in HEAD but not in origin | |
4474 | $ git am mbox # import patches from the mailbox "mbox" | |
4475 | ----------------------------------------------- | |
4476 | ||
2de9b711 | 4477 | Fetch a branch in a different Git repository, then merge into the |
2624d9a5 BF |
4478 | current branch: |
4479 | ||
4480 | ----------------------------------------------- | |
4481 | $ git pull git://example.com/project.git theirbranch | |
4482 | ----------------------------------------------- | |
4483 | ||
4484 | Store the fetched branch into a local branch before merging into the | |
4485 | current branch: | |
4486 | ||
4487 | ----------------------------------------------- | |
4488 | $ git pull git://example.com/project.git theirbranch:mybranch | |
4489 | ----------------------------------------------- | |
4490 | ||
4491 | After creating commits on a local branch, update the remote | |
4492 | branch with your commits: | |
4493 | ||
4494 | ----------------------------------------------- | |
4495 | $ git push ssh://example.com/project.git mybranch:theirbranch | |
4496 | ----------------------------------------------- | |
4497 | ||
4498 | When remote and local branch are both named "test": | |
4499 | ||
4500 | ----------------------------------------------- | |
4501 | $ git push ssh://example.com/project.git test | |
4502 | ----------------------------------------------- | |
4503 | ||
4504 | Shortcut version for a frequently used remote repository: | |
4505 | ||
4506 | ----------------------------------------------- | |
4507 | $ git remote add example ssh://example.com/project.git | |
4508 | $ git push example test | |
4509 | ----------------------------------------------- | |
4510 | ||
4511 | [[repository-maintenance]] | |
fd5b820d | 4512 | === Repository maintenance |
2624d9a5 BF |
4513 | |
4514 | Check for corruption: | |
4515 | ||
4516 | ----------------------------------------------- | |
4517 | $ git fsck | |
4518 | ----------------------------------------------- | |
4519 | ||
4520 | Recompress, remove unused cruft: | |
4521 | ||
4522 | ----------------------------------------------- | |
4523 | $ git gc | |
4524 | ----------------------------------------------- | |
4525 | ||
4526 | ||
e34caace | 4527 | [[todo]] |
fd5b820d MÅ |
4528 | [appendix] |
4529 | == Notes and todo list for this manual | |
6bd9b682 | 4530 | |
03920ac6 | 4531 | [[todo-list]] |
fd5b820d | 4532 | === Todo list |
03920ac6 | 4533 | |
6bd9b682 BF |
4534 | This is a work in progress. |
4535 | ||
4536 | The basic requirements: | |
ecd95b53 BF |
4537 | |
4538 | - It must be readable in order, from beginning to end, by someone | |
4539 | intelligent with a basic grasp of the UNIX command line, but without | |
2de9b711 | 4540 | any special knowledge of Git. If necessary, any other prerequisites |
ecd95b53 BF |
4541 | should be specifically mentioned as they arise. |
4542 | - Whenever possible, section headings should clearly describe the task | |
4543 | they explain how to do, in language that requires no more knowledge | |
4544 | than necessary: for example, "importing patches into a project" rather | |
6127c086 | 4545 | than "the `git am` command" |
6bd9b682 | 4546 | |
d5cd5de4 BF |
4547 | Think about how to create a clear chapter dependency graph that will |
4548 | allow people to get to important topics without necessarily reading | |
4549 | everything in between. | |
d19fbc3c | 4550 | |
1249d8ad | 4551 | Scan `Documentation/` for other stuff left out; in particular: |
ecd95b53 BF |
4552 | |
4553 | - howto's | |
1249d8ad | 4554 | - some of `technical/`? |
ecd95b53 | 4555 | - hooks |
5162e697 | 4556 | - list of commands in linkgit:git[1] |
d19fbc3c BF |
4557 | |
4558 | Scan email archives for other stuff left out | |
4559 | ||
4560 | Scan man pages to see if any assume more background than this manual | |
4561 | provides. | |
4562 | ||
2f99710c BF |
4563 | Add more good examples. Entire sections of just cookbook examples |
4564 | might be a good idea; maybe make an "advanced examples" section a | |
4565 | standard end-of-chapter section? | |
d19fbc3c BF |
4566 | |
4567 | Include cross-references to the glossary, where appropriate. | |
4568 | ||
3dff5379 | 4569 | Add a section on working with other version control systems, including |
9a241220 BF |
4570 | CVS, Subversion, and just imports of series of release tarballs. |
4571 | ||
0b375ab0 | 4572 | Write a chapter on using plumbing and writing scripts. |
d9bd321c BF |
4573 | |
4574 | Alternates, clone -reference, etc. | |
4575 | ||
1cdade2c | 4576 | More on recovery from repository corruption. See: |
efe6de6e OB |
4577 | http://marc.info/?l=git&m=117263864820799&w=2 |
4578 | http://marc.info/?l=git&m=117147855503798&w=2 |